JPH07270155A - Distance sensor - Google Patents

Abstract

PURPOSE:To enable the detecting of condition in which an output exists in an unstable area near a set distance with a distance sensor. CONSTITUTION:An object 4 is irradiated with a parallel light beam 3 through a convergent lens 2 from a projector 1. The reflected light to the object is received with a position detector 6 and the ratio thereof is calculated with a division circuit 10. A comparator 11 compares the ratio with a first threshold Vref1 and judges a far or close position to a set distance to output the results. Second and third thresholds Vref2 and Vref3 are set above and below the first threshold respectively and the first threshold is compared therewith by means of comparators 12 and 13. When the former threshold is within the range of the latter threshold, an unstable area is determined and when it is outside the range, a stable area is determined. Thus, the results are judged to produce an output.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance sensor for optically measuring a distance to a detection target.

[0002]

2. Description of the Related Art Conventionally, as shown in, for example, Japanese Patent Laid-Open No. 57-44809, a distance measuring device using a trigonometric method is known as a device for detecting a distance to an object. In this device, a light emitting element such as a light emitting diode is irradiated as a parallel light beam in the direction in which the distance should be detected, and a light receiving element capable of detecting the irradiation position of reflected light from an object, for example, a position detection element ( A position sensitive device (PSD) is provided, and an analog signal corresponding to the distance to the object is obtained by, for example, calculating the ratio based on the current output obtained at both ends of the output.

Further, when the distance output obtained from the light receiving portion of the distance sensor is discriminated at a predetermined level to detect the distance from the predetermined distance, the output of the distance sensor is given to a comparator and a predetermined value is determined based on the threshold value. A distance sensor is also used that obtains a distance determination signal by determining distance from the distance.

[0004]

However, according to such a conventional distance sensor, it is not possible to distinguish whether the distance output is in a stable state or an unstable state. If the object to be detected is in an unstable region near the set distance, there is a drawback that the output may be easily inverted due to temperature fluctuations, optical axis shifts, and the like.

The present invention has been made in view of the above problems of the conventional distance sensor. In the distance sensor as well, the distance sensor is in an unstable region near the set distance or is sufficiently separated from the set distance. The technical issue is to be able to determine whether or not it is in the stable region.

[0006]

According to the present invention, there is provided a light projecting portion having a light projecting element, an output signal which is arranged so as to have a predetermined distance from the light projecting portion, receives reflected light from an object, and which corresponds to a light receiving position. To obtain a signal, a calculation unit that calculates and outputs a signal corresponding to the distance to the object based on the output of the light reception unit, and the output from the calculation unit is discriminated by a predetermined first threshold value to determine that the object has a predetermined distance. A distance sensor having a determination unit that determines whether the distance is farther or closer, and an unstable region before and after a predetermined distance by discriminating the output from the calculation unit with thresholds set above and below the first threshold. And an unstable region detection unit that detects the presence of an object in the device and obtains a signal indicating the presence or absence of the margin of the determination result of the determination unit.

[0007]

According to the present invention having such a feature, a signal corresponding to the distance to the object is output by projecting light from the light projecting portion to the detection region and by the light receiving position obtained by the light receiving element of the light receiving portion. . Then, the received light signal is given to the discriminating means to discriminate the distance from the predetermined distance. Further, the output from the calculation unit is discriminated by the threshold values set above and below the first threshold value, and when it is within this range, the object exists in the unstable region,
I am trying to output this.

[0008]

1 is a diagram showing the configuration of a distance sensor according to an embodiment of the present invention. As shown in the figure, the distance sensor has a light projecting element 1 and a focusing lens 2 as a light projecting section, and the light of the light projecting element 1 is transmitted through the focusing lens 2 to a parallel light beam 3
Is emitted in the direction in which the distance to the object 4 should be detected. Then, a condenser lens 5 is arranged so as to intersect the light beam 3 at a predetermined distance from the focusing lens 2 so as to intersect the light beam 3 at a predetermined angle, and a one-dimensional position detecting element (PSD) behind the condenser lens 5. 6 is provided. A bias power supply 7 is connected to the center of the position detection element 6, and two different current outputs are provided to both ends of the element in accordance with the light irradiation position. The respective current outputs of the position detection element 6 are given to the I / V converters 8 and 9, and the voltage signal thereof is given to the division circuit 10. In this way, the position signal can be obtained from the division circuit 10 according to the light receiving position of the reflected light corresponding to the distance to the object. Here, the condenser lens 5 and the position detection element 6 constitute a light receiving section that receives the reflected light and obtains an output signal corresponding to the light receiving position, and the I / V converters 8 and 9 and the division circuit 10 receive the light. The arithmetic unit is configured to calculate and output a distance signal to the object based on the output of the unit.

The output of the division circuit 10 is the comparator 1
1 to 13 are given. The comparator 11 constitutes a discriminating means for discriminating whether the object is closer or farther than the set distance by discriminating the distance signal to the object with a predetermined first threshold value Vref1. Also comparator 12
And 13 are the second and third thresholds V above and below the threshold Vref1, respectively.
Ref2 and Vref3 are set, and an unstable region detection unit that determines whether or not there is a margin depending on whether it is in an unstable region near the set distance or outside this range is configured.
The outputs of the comparators 12 and 13 are exclusive OR circuits 14
And an unstable state is detected when an output is obtained from either one. The outputs of the I / V converters 8 and 9 are given to the adder 15 and added, and the outputs are given to the comparators 16 and 17. The comparator 16 determines whether or not the input level of the division circuit 10 is sufficiently high and has reached the amount of received light to obtain a distance output, and the threshold Vref4 of the amount of received light is set. Further, the comparator 17 determines whether or not the threshold value Vref5 is set to a level higher than that and a stable split calculation force is obtained. The output of the comparator 16 is externally output as a light reception output signal, and the comparator 17 is externally provided as an output of a stable light reception signal.

In the present invention, as shown in FIGS. 2 and 3, a distance signal, a light receiving signal and their unstable outputs are obtained corresponding to the distance to the object. That is, the distance to the object is
If it changes with time as shown in (a),
When the distance signal from the division circuit 10 exceeds the threshold value Vref1 set in the comparator 11, a distance determination signal as shown in FIG. 2B is obtained. And the comparator 12
When the level is higher than the threshold Vref2 of the comparator 13 or the threshold Vref3 of the comparator 13, the outputs are obtained from the comparators 12 and 13, respectively, and the output is obtained as the exclusive OR output thereof.
An unstable output is obtained as shown in (c). When this signal is on, it is between the threshold values Vref2 and Vref3, and
This indicates that the distance signal in (b) is in an unstable region, and when this output is OFF, it is shown that the distance determination signal is sufficiently close to or far from the set distance and the reliability of the distance determination signal is high.

Next, FIG. 3A is a graph showing a temporal change in the amount of received light. If the amount of received light which is the output of the adder 15 exceeds the set value Vref4, the received light output is obtained from the comparator 16. It is shown that the output from the division circuit 10 is a meaningful signal. When the amount of received light exceeds the threshold value Vref5 which is higher than the set value Vref4, a stable received light signal is obtained as shown in FIG. Therefore, it is shown that the received light amount is also in the stable region. These outputs may be displayed as they are, for example, by a light emitting diode or the like, or may be displayed by lighting, blinking, or extinguishing a distance determination signal, a stable state, an unstable state, or the like. Alternatively, as shown by the broken line in FIG. 1, the output of the exclusive OR circuit 14 and the output of the comparator 17 may be given to the AND circuit 18, and the logical product of these may be taken for stable display. Further, when changing the threshold Vref1 of the comparator 11, the upper and lower thresholds Vref2 and Vref3 may be changed at the same time, and when the threshold Vref4 is set, the threshold Vref5 of a higher level may be changed at the same time. You may be able to set it.

In this embodiment, two comparators whose thresholds are set above and below the threshold of the discriminating means for obtaining the distance signal are used to give their exclusive OR, but the output of each comparator and the distance discrimination It may be outputted by discriminating which side is closer by exclusive OR with the signal.

Further, in this embodiment, the distance signal is obtained by converting the current output across the position detecting element (PSD) into a voltage signal and giving it to the division circuit. May be given to the division circuit to obtain the distance signal, or the addition signal and either one of the I / V conversion outputs may be given to the division circuit to obtain the distance signal.

Further, although the present embodiment shows the distance sensor using the position detecting element as the light receiving element, a MOS image sensor or a CCD sensor may be used as the light receiving sensor. In this case, only the stable / unstable state of the distance signal is detected.

[0015]

Therefore, according to the present invention, it is determined whether the object is sufficiently closer or farther than the set distance by determining not only the distance determination signal obtained by the determination means but also whether or not it is in the unstable region around it. can do. Therefore, when detecting an object that passes a predetermined distance, it is possible to set a stable state in which the distance signal is "far" when the background is only so that the background is not detected when there is no object. In this way, even if the distance discrimination output fluctuates due to temperature drift or the like, a "far" signal can be output if an object is not detected, so it is possible to prevent malfunction.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a distance sensor according to an embodiment of the present invention.

FIG. 2 is a graph showing a distance signal of a distance sensor with respect to a change in distance to an object, a distance determination signal corresponding to the distance signal, and an unstable output.

FIG. 3 is a graph showing a received light output and a stable output thereof with respect to a change in the amount of received light.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Projection element 6 Position detection element 8, 9 I / V converter 10 Division circuit 11-13, 16, 17 Comparator 14 Exclusive OR circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hidetoshi Matsumoto 10 Odoron-cho, Hanazono Tadodo-cho, Ukyo-ku, Kyoto Prefecture Kyoto

Claims (1)

[Claims] 1. A light projecting section having a light projecting element, a light receiving section arranged to have a predetermined distance from the light projecting section to receive reflected light from an object and obtain an output signal corresponding to a light receiving position.
A calculation unit that calculates and outputs a signal corresponding to the distance to the object based on the output of the light receiving unit, and the output from the calculation unit are discriminated by a predetermined first threshold to determine whether the object is far or nearer than a predetermined distance. And a discriminating unit for discriminating the output from the arithmetic unit with threshold values set above and below the first threshold value to discriminate an object in an unstable region before and after the predetermined distance. An unstable region detection unit that detects the existence, and obtains a signal indicating the presence or absence of the margin of the determination result of the determination unit,
A distance sensor having: