JP2581480B2 - Distance sensor - Google Patents

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 an object to be detected.

[0002]

2. Description of the Related Art As disclosed in, for example, Japanese Patent Application Laid-Open No. 57-44809, a distance measuring device based on 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 a direction in which a distance is to be detected, and a light receiving element capable of detecting an irradiation position with reflected light from an object, for example, a position detecting element A position sensitive device (PSD) is provided, and an analog signal corresponding to the distance to the object is obtained by calculating, for example, the ratio based on the current output obtained at both ends of the output.

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 a predetermined distance, the output of the distance sensor is supplied to a comparator, and a predetermined value is determined based on the threshold value. A distance sensor that determines a distance from a distance and obtains a distance determination signal is also used.

[0004]

However, according to such a conventional distance sensor, it has not been possible to discriminate whether the distance output is in a stable state or an unstable state. If the object to be detected is located in an unstable area near the set distance, there is a disadvantage that the output may be easily inverted due to temperature fluctuation, optical axis shift or the like.

The present invention has been made in view of such a problem of the conventional distance sensor, and the distance sensor is also located in an unstable area near the set distance or sufficiently away from the set distance. It is a technical object to be able to determine whether or not it is in a stable region.

[0006]

According to the present invention, there is provided a light projecting section having a light projecting element, and an output signal arranged at a predetermined distance from the light projecting section to receive reflected light from an object and correspond 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 reception unit; and discriminates the output from the calculation unit with a predetermined first threshold to determine whether the object has a predetermined distance. A discriminating unit for discriminating whether the distance is farther or closer, wherein an unstable area before and after a predetermined distance by discriminating an output from the calculating unit with a threshold value set above and below the first threshold value And an unstable area detecting section that detects the presence of an object in the area and obtains a signal indicating whether or not there is a margin in the discrimination result of the discriminating section.

[0007]

According to the present invention having the above features, a signal corresponding to the distance to the object is output according to the light receiving position obtained by projecting light from the light projecting unit to the detection area and being obtained by the light receiving element of the light receiving unit. . Then, the light receiving signal is given to the determining means, and the distance from a predetermined distance is determined. Also, the output from the calculation unit is discriminated by thresholds set above and below the first threshold, and when the object is within this range, the object is present in the unstable region.
This is output.

[0008]

FIG. 1 is a diagram showing the configuration of a distance sensor according to one embodiment of the present invention. As shown in the figure, the distance sensor has a light projecting element 1 and a converging lens 2 as a light projecting unit, and the light of the light projecting element 1 is converted into a parallel light beam 3 via the converging lens 2.
Is irradiated in the direction in which the distance to the object 4 is to be detected. A condensing lens 5 for condensing reflected light, which is arranged to intersect the light beam 3 at a predetermined angle at a predetermined distance from the converging lens 2, and a one-dimensional position detecting element (PSD) behind the condensing lens 5 6 are provided. The position detecting element 6 has a bias power supply 7 connected to the center thereof, and provides two different current outputs to both ends of the element in accordance with the light irradiation position. The respective current outputs of the position detecting element 6 are applied to I / V converters 8 and 9, and the voltage signals thereof are applied to a dividing circuit 10. In this way, a position signal can be obtained from the division circuit 10 based on the position of the reflected light received corresponding to the distance to the object. Here, the condenser lens 5 and the position detecting element 6 constitute a light receiving section for receiving the reflected light and obtaining an output signal corresponding to the light receiving position, and the I / V converters 8, 9 and the dividing circuit 10 receive the reflected light. And a calculating unit configured to calculate and output a distance signal to the object based on the output of the unit.

The output of the dividing circuit 10 is the comparator 1
1-13. The comparator 11 constitutes a discriminating means for discriminating a distance signal to the object by a predetermined first threshold value Vref1 to determine whether the object is closer or farther than the set distance. Comparator 12
And 13 are the second and third thresholds V above and below the threshold Vref1, respectively.
ref2 and Vref3 are set, and constitutes an unstable area detection unit that determines whether or not there is a margin depending on whether the area is in an unstable area near the set distance or outside this range.
The outputs of the comparators 12 and 13 are output from an exclusive OR circuit 14
And an unstable state is detected when an output is obtained from one of them. The outputs of the I / V converters 8 and 9 are provided to an adder 15 for addition, and the output is provided to comparators 16 and 17. The comparator 16 determines whether or not the input level of the division circuit 10 is sufficiently high to reach a light receiving amount at which a distance output can be obtained, and a threshold Vref4 of the light receiving amount is set. Further, the comparator 17 determines whether or not the threshold Vref5 is set to a higher level and a stable split calculation power is obtained. The output of the comparator 16 is externally output as a light receiving output signal, and the comparator 17 is externally provided as a stable light receiving signal output.

In the present invention, as shown in FIGS. 2 and 3, a distance signal, a light receiving signal, and an unstable output thereof 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 dividing 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
If the level is higher than the threshold value Vref2 of the comparator 13 or the threshold value Vref3 of the comparator 13, the output is obtained from the comparators 12 and 13, respectively.
An unstable output is obtained as shown in FIG. When this signal is on, it is between the threshold values Vref2 and Vref3,
(B) indicates that the distance signal is in an unstable region, and when this output is off, it indicates that the distance determination signal is sufficiently close or farther than the set distance and the reliability of the distance determination signal is high.

Next, FIG. 3A is a graph showing a temporal change of the received light amount. If the received light amount output from the adder 15 exceeds the set value Vref4, a light received output is obtained from the comparator 16. This indicates that the output from the division circuit 10 is a meaningful signal. When the amount of received light exceeds a threshold value Vref5 higher than the set value Vref4, a stable received light signal is obtained as shown in FIG. Accordingly, it is shown that the amount of received light 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 turning on, blinking, or extinguishing a distance determination signal, a stable state, an unstable state, and the like. Also, as shown by a broken line in FIG. 1, the exclusive OR circuit 14 and the output of the comparator 17 may be supplied to an AND circuit 18 to obtain a logical product of them and perform stable display. When the threshold value Vref1 of the comparator 11 is changed, the upper and lower threshold values Vref2 and Vref3 may be simultaneously changed in conjunction with each other, and when the threshold value Vref4 is set, a higher level threshold value Vref5 is simultaneously set. It may be settable.

In this embodiment, two comparators having threshold values set above and below the threshold value of the determination means for obtaining the distance signal are used to give an exclusive OR of them. It is also possible to determine which side is closer by exclusive OR with the signal and output it.

In this embodiment, the current output at both ends of the position detecting element (PSD) is converted into a voltage signal and applied to a dividing circuit to obtain a distance signal. May be given to a division circuit to obtain a distance signal, or the addition signal and one of the I / V conversion outputs may be given to a division circuit to obtain a distance signal.

Further, in this embodiment, a distance sensor using a position detecting element as the light receiving element is shown, but 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 close or farther than the set distance by determining not only the distance determination signal obtained from the determination means but also whether or not the object is in an unstable area around the signal. can do. Therefore, when an object passing a predetermined distance is detected, the background signal can be set in advance in a stable state with the distance signal being “far” 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 no object is detected, so that malfunction can be prevented.

[Brief description of the drawings]

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

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

FIG. 3 is a graph showing a light receiving output and a stable output with respect to a change in a light receiving amount.

[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

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Hidetoshi Matsumoto, Inventor Omron Corporation 9212 (JP, A) JP-A-62-150115 (JP, A) JP-A-62-141712 (JP, U)

Claims (1)

(57) [Claims] A light-emitting unit having a light-emitting element; a light-receiving unit arranged at a predetermined distance from the light-emitting unit 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 determines whether the object is farther or shorter than a predetermined distance by discriminating the output from the calculation unit with a predetermined first threshold value And a discriminating unit that discriminates between the first and second thresholds. An unstable area detection unit that detects the presence of the signal, and obtains a signal indicating whether or not there is a margin in the determination result of the determination unit;
A distance sensor comprising: