JPS60235083A - Reflective type photoelectric sensor - Google Patents

Abstract

PURPOSE:To make it possible to determine the position of light reflected in a front space, by scanning the definite angular range in the front space by luminous flux. CONSTITUTION:A light source 1 equipped with a luminous flux scanning apparatus is constituted so that the definite angular range omega1 of a front space is scanned by luminous flux and driven by pulse line like drive power from a light source drive power source 13 to successively scan the front space. If an obstruction 11 is present in this front space, the reflected light from the obstruction 11 is detected by a light receiving element 12 and the photoelectric conversion output thereof is amplified by a photoelectric conversion output processing circuit 14. The output of the circuit 14 and the timing signal from the power source 13 are connected to a detection object discrimination circuit 15 and the angle or distance of light reflected in the front space is discriminated. Now, if the obstruction is present in the range of omega2 within the definite angular range of the front space, reflection is generated only when the range of the angle omega2 is scanned by luminous flux and detected by the element 2. Therefore, output appears from the circuit 14 only for said period and the circuit 15 judges that there exists an obstruction object in the range of the angle omega2 within the front space omega1.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a reflective photoelectric sensor, and more specifically, to a reflective photoelectric sensor that can be used to detect obstacles located at various distances.

(Prior technology) Obstacle detection using a conventional reflective photoelectric sensor
This will be briefly explained with reference to the drawings.

In order to increase the reach distance, the light from the light source 101 is made into a nearly parallel beam by the projection lens 102, and is projected toward the obstacle 103.

The reflected light from the obstacle 103 is photoelectrically converted by the light receiving element 105 via the light receiving lens 104.

This photoelectric conversion output is an amplification and signal component extraction circuit 107
The obstacle detection and determination circuit 108 detects the presence of the obstacle.

That is, the reflected light from the light source 101 is transmitted to the light receiving element 10.
5 and detects the obstacle 103 with or without a detection current, the following problems arise.

(2) It goes without saying that the obstacle 103 cannot be detected unless it is in a position where the light beam from the light source 101 hits.

As described above, the light from the normal light source 101 is turned into a nearly parallel beam by the projection lens 102 and projected toward the obstacle 103 in order to increase the reach distance, so the detection field of view is very narrow.

(2) If there is a wall or object with high reflectivity behind the obstacle 103, it may not be possible to distinguish the light reflected from the obstacle 103, resulting in a malfunction.

(Object of the Invention) An object of the present invention is to provide a reflective photoelectric sensor that can determine from which part of the space in front the reflected light is coming from.

(Structure of the Invention) In order to achieve the above object, a reflective photoelectric sensor according to the present invention includes a light source with a beam scanning device that scans a predetermined angular range of a space in front with a beam of light, and a light source driving power source that drives the light source. a light-receiving element that photoelectrically converts the reflected light from the object scanned by the light beam from the light source; and the output of the light-receiving element is synchronized with the drive output of the light source driving power source and processed to determine which area in the space in front of the object. It consists of a discrimination circuit that discriminates whether it is a reflection from

(Example) The present invention will be described in more detail below with reference to the drawings and the like.

FIG. 1 is a layout diagram showing the basic configuration of a reflective optical sensor according to the present invention, in which (A) is a planar layout diagram, (B) is a left side layout diagram, and (C ) is a block diagram of the circuit.

The light source 10 with a beam scanning device is configured to scan a predetermined angular range (ω1) in the space in front with a beam of light.

This light source 10 with a beam scanning device is driven by a pulse train of driving power from a light source driving power source 13 and sequentially scans the space in front of it.

If there is an obstacle 11 in this forward space, the reflected light from the obstacle 11 is detected by the light receiving element 12 and photoelectrically converted.

The photoelectric conversion output of the light receiving element 12 is amplified by a photoelectric conversion element output processing circuit 14.

The output from the photoelectric conversion element output processing circuit 14 and the timing signal from the light source driving power source 13 are connected to the detection target discrimination circuit 15, and it is possible to discriminate from which angle or distance in the space in front of the light the reflection occurred. be done.

Now, the obstacle 11 is within a certain angular range (ω1) of the space in front of it.
If the beam exists within the range (ω2) of
) occurs and is detected by the light receiving element 12. The photoelectric conversion element output processing circuit 1 only during that period.
Output appears from 4.

The detection object determination circuit 15 refers to the output from the photoelectric conversion element output processing circuit 14 and the timing signal from the light source driving power source 13, and determines that an obstacle exists in (ω2) in the forward space (ω1). be able to.

FIG. 2 is a block diagram showing a first embodiment of the reflective optical sensor according to the present invention.

In this embodiment, an infrared light emitting diode 17 (for example, Hamamatsu Photonics' L
i2O2) is used.

This infrared light emitting diode 17 is caused to emit pulsed light by a light emitting diode drive circuit 23.

This pulsed light emission is made into a state close to a parallel light beam by the projection lens 18.

The rotating prism 19 is rotated by a motor 24 around an axis parallel to the base line (distance B connecting the light emitting lens 18 and the light receiving lens 21).

As a result, the light beam from the infrared light emitting diode 17 is deflected in a direction perpendicular to the plane of the paper.

In order to establish this deflection frequency and synchronization, a synchronization detection sensor 25 of the rotating prism 16 is used.

When an obstacle 20 comes within the deflection angle of this light beam, it is reflected on the surface of the obstacle 20, and a part of this reflected light is transmitted to a one-dimensional semiconductor device detection device 22 (for example, 31743 manufactured by Hamamatsu Photonics Co., Ltd.) using a light receiving lens 21. -01) is focused on the light receiving surface.

Now, the distance to the obstacle is determined, the base line length is B, the focal length of the light receiving lens is f, and the electrode 22 of the one-dimensional semiconductor device detector 22 is
a, 22b is the distance from the electrical center position of the C1 semiconductor device detector 22 (normally the point equally divided between the electrodes) to the center of gravity of the focused spot light, then the following (
1) The formula holds true.

x= (B-f)/L (1) Furthermore, there is a relationship between the reflected light detection current tl, +2 obtained from the electrode of the semiconductor device detector 22 and X as shown in the following equation (2). To establish.

i2/1l= (C/ 2 + x) / (C/ 2-x) =-1
21 By calculating the ratio of the reflected light detection current from the semiconductor device detector 22 +1°12, tl, ), (2'1), the distance to the obstacle can be obtained.

The output current of the semiconductor device detector 22 is input to the arithmetic unit 26 and i2/il is determined.

FIG. 3 is a block diagram showing an embodiment of an arithmetic unit that processes the output of a semiconductor device detector.

The photocurrent obtained from the output terminal of the semiconductor device detector 22 includes an external light component in addition to the pulsed light from the light source reflected from the obstacle.

Therefore, the signal component extraction/amplification circuits 33 and 34 extract and amplify only the signal component.

Then, the arithmetic circuit 35 executes the arithmetic operation of l 2 /f 1 . This calculated value is held in a sampling hold circuit 36.

The discrimination circuit 27 calculates L shown in equation (1) from the i 2 /i 1, and 12. From the period in which 11 exists, it is determined and output which space the reflection is from.

FIG. 4 is a perspective view showing a light source section and a light receiving section of a second embodiment of the reflective optical sensor according to the present invention.

In the first embodiment, an infrared light emitting diode 17 with one light emitting point is used, and a rotating prism 19 and its driving motor 24 are used to swing a luminous flux in a direction perpendicular to the plane of the paper.

In this second embodiment, no such mechanically moving parts are necessary.

LED Chip 7 β1. A multi-point light source 28 with 2 to βn arranged perpendicular to the base line B is provided, and this LED chip e
1 to en are emitted in a time-division manner.

If the light is projected forward by the projection lens 29, the space in front can be scanned by the light flux.

A semiconductor device detector 31 is placed at a position separated from the multi-point light source 28 by a base line length B.

Lens 30 is a condenser lens.

FIG. 5 is a circuit diagram showing an embodiment of the multi-point light emitting light source and a driver circuit for lighting the multi-point light emitting light source in a time-division manner.

FIG. 6 is a timing chart of the driver circuit.

When n clocks are input to the driver circuit 37, a reset (REsET) is applied, and output terminals turn on in order from output terminal 01.
The output state becomes HIGH in a time-division manner. In this order, the transistors Tr1 to Trn are turned on, and the LEI) chips ρ1 to ρn are caused to emit light in a time-division manner. .

As shown in Figure 4, the light emitting point of the light source is relative to the base line length B.
arranged at right angles.

The total length of this array of light emitting points is assumed to be 4.

On the other hand, a pair of electrodes 31a of the semiconductor device detector 31
, 31b is arranged in the base line length direction, and the electrode spacing is C.
Let W be the length of one electrode.

The following (3
) equation is given.

W>l (3) As a result, all the reflections caused by the light emission of all the LED chips reach the effective light receiving surface of the semiconductor device detector 31.

If the closest distance to the obstacle is Lmin, then from equation (1), the maximum moving distance x max of the reflected spot light is (4
) becomes the formula.

xmax=(B-f)/Lmin...(4
) When the diameter of the reflected spot light focused on the semiconductor device detector 31 by the light receiving lens 30 is d, the reflected spot light is focused on the electrodes 31a and 31b of the semiconductor device detector 31.
In order to stay within the range, it is necessary to satisfy the condition of equation (5).

C≧2 x max + d − ·151 The output current of the semiconductor device detector 31 is processed by the arithmetic device and discrimination device shown in FIGS. 2 and 3 above.

Next, an example of the operation of this embodiment sensor will be explained.

When a clock signal is input to the driver circuit 37 shown in FIG. 5, the light emitting points of the light source 28 are sequentially turned on in a time-division manner.

FIG. 7 shows the output waveform of the arithmetic unit 26.

This indicates that the reflected photocurrent is in a zero state at the time when the clock signals (■) and (2) are input. In other words, the distance to the obstacle is infinite. Next, the clock ■, ■,
When (2) is input, the pulsed light flux from the light source hits the obstacle, and a reflected photocurrent is obtained from the semiconductor device detector 31.

When the clock signals ■, ■, . . . , ■ are input, the reflected photocurrent becomes zero again.

The following three pieces of information can be obtained from this output waveform Vout.

■) The clock signal divides the detection field of view into n, and from which position of the clock signal Vout(i2/i
The direction in which the obstacle exists can be determined by the number of times the voltage (corresponding to 1) rises and falls.

2) For the same reason as 1), the width OW of the obstacle can be known.

3) The distance to the obstacle can be known from the magnitude of the amplitude Vout of the output calculation value.

That is, (11, (From equation 21, the output calculation value Vout is determined by the distance to the obstacle.

(Effects of the Invention) Since the reflective photoelectric sensor according to the present invention is configured to scan the space in front with a light beam, it is possible to obtain information such as the distance, position, and size of the object in front.

[Brief explanation of the drawing]

FIG. 1 is a layout diagram showing the basic configuration of a reflective optical sensor according to the present invention, in which (A) is a planar layout diagram, (B) is a left side layout diagram, and (C ) is a block diagram of the circuit. FIG. 2 is a block diagram showing a first embodiment of the reflective optical sensor according to the present invention. FIG. 3 is a block diagram showing an embodiment of the arithmetic unit of the semiconductor device detector of the reflective optical sensor according to the present invention. FIG. 4 is a perspective view showing a second embodiment of the reflective optical sensor according to the present invention. FIG. 5 is a block diagram showing an embodiment of the light source and its driver used in the second embodiment. FIG. 6 is a timing chart showing the operation of the driver. FIG. 7 is a waveform diagram showing an example of an output signal waveform. FIG. 8 is a block diagram showing an obstacle sensor using a conventional reflective photoelectric sensor. 10... Light source with beam scanning device 11... Detection target object 12... Photoelectric element 13... Light source driving power supply 14... Photoelectric conversion element output processing circuit 15... Detection target discrimination circuit 17...・Light-emitting diode 18... Light emitting lens 19
... Rotating prism 20 ... Obstacle 21 ... Light receiving lens 22 ... Semiconductor device detector 23 ... LED driver circuit 24 ... Drive motor 25 ... Rotation synchronization detection sensor 26 ...・Arithmetic unit 27...Discrimination circuit 28...Light source 29...Light emitting lens 30...Light receiving lens 31...Semiconductor device detector 33.34...Signal component extraction/amplification circuit 35... - Arithmetic circuit 36...Sample hold circuit 37...Driver circuit 101...Light source 102...Light projection lens 103...
・Obstacle 104... Light-receiving lens 105... Light-receiving element 106... Driver circuit Patent applicant Hamamatsu Photonics Co., Ltd. Representative Patent attorney Hisashi Inoro + 3 Figure

Claims (1)

[Scope of Claims] [1] A light source with a beam scanning device that scans a predetermined angular range of space in front with a beam of light, a light source driving power source that drives the light source, and an object scanned by the beam of light from the light source. A light receiving element that photoelectrically converts reflected light from the light source, and a discrimination circuit that processes the output of the light receiving element in synchronization with the drive output of the light source driving power source to determine from which area in the space in front the light is reflected. Reflective optical sensor. (2) The light source with the beam scanning device includes a light emitting diode;
2. The reflective optical sensor according to claim 1, further comprising: a lens that converts the light flux of the light emitting diode into a parallel light beam; and an optical device disposed in front of the lens to vibrate the light flux. (3) The reflective optical sensor according to claim 2, wherein the light receiving element is a one-dimensional semiconductor device detector arranged in the baseline direction at a position a certain baseline length away from the light source with the beam scanning device. (4) The light source such as the light beam scanning device is composed of a large number of light emitting elements arranged in a line and one lens for forming parallel light arranged in front of the light emitting elements, and each light emitted by the light source driving power source is 2. The reflective optical sensor according to claim 1, wherein the light beam scans a predetermined angular range in the space in front of the device by lighting the elements in a time-divisional manner. (5) The light receiving element is a one-dimensional semiconductor device detector arranged in the baseline direction at a position a certain baseline length away from the optical scanning surface of the light source with the beam scanning device, and the width W in the direction perpendicular to the position detection direction is as described above. 5. The reflective optical sensor according to claim 4, wherein the distance between both ends of the plurality of light emitting elements is greater than 4.