JPH06118178A - Object detector - Google Patents

Abstract

PURPOSE:To reduce erroneous functioning and make setting easy by providing a means for measuring the distance to an object to be detected from the incidence angle of reflection light to a light receiver part and detecting the existence or pass of the object when the measured distance becomes closer than the distance to the background. CONSTITUTION:By intermittently emitting pulse signals with a timing controller 2, an LED drive circuit 3 is driven and infrared light is irradiated from an infrared LED to an object to be detected through a casting lens 8. The reflection light having passed through a receiver lens 6 is received with a PSD (position sensing element) and after amplifying 8, the distance is calculated 9 and compared with the distance to the background with a distance comparator 10. If the distance to the detected body is closer, existence or passing of the object is detected. By amplifying 11 and comparing 12 the received light, the existence of the object is detected when the reflection light is below a certain level for the received light. By this method using infrared beam, interference with other light is avoided and the part to be detected can be exactly set owing to a narrow detection area.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an object detection device for detecting the presence or absence of an object and passage, and more particularly to a detection device for vehicle inventory detection or passage detection.

[0002]

2. Description of the Related Art Conventionally used vehicle detection devices include a loop coil system, an ultrasonic wave reflection system, and a light shielding detection system. The method using the loop coil has a problem that the installation cost increases because the loop coil must be buried in the ground. The ultrasonic reflection method has a problem that it is easily affected by an object around the detection device due to its wide detection zone, is limited in installation, and often causes malfunctions due to changes in air humidity and wind. Further, the method based on light-shielding detection has a problem in that it is often difficult to install because the light projecting section and the light receiving section are installed, and even when the reflective panel is used, the reflective panel may not be installed.

In particular, the ultrasonic method has the following drawbacks.・ Other ultrasonic devices or ultrasonic sensors worked together to cause malfunction. In the case of ultrasonic waves, 4m
There were restrictions such as the need to install them further apart.・ When an air fault such as an air curtain or an air conditioner with a temperature difference crossed the detection range, it malfunctioned.・ If there was an extreme extraneous ultrasonic wave (such as a brake sound), it was malfunctioning.・ When the shape of an object is inclined, it may not be detected. For example, if the vehicle is installed at an angle due to detection,
Ultrasonic reflection is reflected in the other direction, so it is not detected.・ I was erroneously detecting that there was an object such as a duct or pipe near the ultrasonic sensor.

[0004]

The problem to be solved by the present invention is to eliminate the influence of objects around the detection device, to facilitate the installation, and to reduce malfunctions.

[0005]

In order to solve the above-mentioned problems, an object detecting device of the present invention comprises a light projecting portion and a light receiving portion which are installed at a fixed interval, and which emits light from the light projecting portion. An object is provided when a distance measuring means for measuring the distance of the detected object by the incident angle of the reflected light from the detected object with respect to the light receiving part is provided, and the distance measured by the distance measuring means becomes shorter than the background distance. The detection means for detecting the presence or passage of With this device, it may not be possible to measure the distance when an object with a low reflectance comes in.Therefore, the presence or passage of an object is detected even when the level of the incident light on the light receiving part becomes lower than the level of the incident light on the background. It is preferable to do so.

[0006]

[Function] When there is no detected object, the distance from the light projecting portion to the background is measured by the reflected light from the background, but when the detected object is present, the distance closer than the distance to the background is measured. Therefore, the presence or absence or passage of the detected object is detected by the change in the distance. If an object with a very low reflectance is present, the level of reflection from the background will be lower, so the presence of the object is also detected.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on the embodiments shown in the drawings. FIG. 1 is a block diagram of an object detection device according to the present invention. In the figure, 1 is an intermittent oscillator, 2
Is a timing control circuit, 3 is an LED drive circuit, 4 is an infrared LED, 5 is a light projecting lens, 6 is a light receiving lens, and 7 is PS.
D (Position Sensitive Device), 8 is an amplifier, 9 is a distance calculation circuit, 10 is a distance comparator, 11 is a light receiving amplification circuit,
Reference numeral 12 is a received light quantity comparator, 13 is a coupling / timer circuit, 14 is a distance comparator operation confirmation LED, and 15 is a received light quantity comparator operation confirmation LED.

Before explaining the operation, the principle of distance measurement by PSD will be described. FIG. 2 is a diagram for explaining the operation of the PSD. The PSD outputs 1 depending on the position where the spot light strikes.
And the current ratio of the output 2 changes. When the spot light hits the center of the light receiving surface, the current I ₁ of the output ₁ and the current I _{2 of the} output 2 become equal, but when shifted to the right, I ₁ <
It becomes I ₂ , and when it shifts to the left, I ₂ <I ₁ . I ₁ , I
The rate of increase or decrease of ₂ is proportional to the deviation of the spot light from the center.

The relationship between the spot light position and I ₂ / I ₁ is given by the following equation and is not affected by the intensity of the spot light. However, if the light is too weak, noise increases and the resolution deteriorates. _{I 2 / I 1 = (C} / 2 + d) / (C / 2-d) = {1 + d / (C / 2)} / {1-d / (C / 2)} (1) where, C is received The surface length, d, is the position from the center of the light receiving surface to the spot light.

By utilizing the fact that the PSD can obtain a linear relationship between the spot light position and the output current, the distance L to the detected object can be measured by the triangulation method as shown in FIG. When the infrared light of the light projecting LED is converged by the light projecting lens and made into a thin beam light and hits the detected object, the spot light reflected by the detected object forms a real image on the light receiving surface of the PSD by the light receiving lens. In FIG. 3, the intensity center position d of the spot light is inversely proportional to the distance L to the object to be detected, and the closer it is, the larger d becomes. This relationship is expressed by the following equation. f / L = d / S (2)

The relationship between the PSD output currents I ₁ and I ₂ is as follows. I ₁ ∝ C / 2-d = C / 2−f · S / L (3) I ₂ ∝ C / 2 + d = C / 2 + f · S / L (4) ∴I ₂ / I ₁ = (C / 2 + f · S / L) / (C / 2-f · S / L) = (C · L / 2 + f · S) / (C · L / 2−f · S) (5)

When the equation (5) is calculated, an output proportional to 1 / L is obtained as shown in FIG. Since the expression (5) is determined only by the base line length S, the mechanical position f between the light receiving lens and the PSD, and the PSD light receiving surface length C, the spot light due to the difference in the reflectance of the object to be detected and the deterioration of the light emitting LED over time. The distance can be measured regardless of the strength of.

In this way, the distance can be measured using the PSD. An infrared LED is used as a light emitting LED to distinguish it from external light, and a visible light cut filter is inserted in front of the light receiving surface of the PSD. Furthermore, the light emitting LED is pulse-driven,
Only the change from that when no light is projected is extracted to distinguish it from outside light.

Returning to FIG. 1, the distance comparator 10 compares the calculated distance with the distance of the background (including infinite length) (distance when there is no object to be detected), and outputs an output if the distance is short. Further, the received light amount comparator 12 outputs an output when the reflected light is equal to or less than a constant received light amount. This is because when the surface of the object to be detected absorbs light, the amount of received light is lower than the amount of reflected light from the background. In this case as well, since it is assumed that an object exists, the combination / timer circuit 13 takes the logical sum of the output of the distance comparator 10 and outputs the object detection signal. In order to remove noise and malfunction, the combination / timer circuit 13 operates as a timer. If the time period is set long, no output signal will be output when a simple object passes, and if it is set short, an output signal will be output even when passing.

FIG. 5 shows an example in which the present invention is applied to a vehicle detection device in a parking lot. FIG. 5A shows the case of an empty vehicle, and infrared rays projected from the object detection device 21 attached to the ceiling of the parking lot are reflected on the floor surface and enter the light receiving section. At this time, the distance comparator 1 of FIG.
The variable resistor VR ₁ of 0 is adjusted, the LED 14 for checking the operation of the distance comparator is once turned on, and then the variable resistor VR ₁ is adjusted in the reverse direction to stop when the LED 14 is turned off. Then, when a blank sheet is placed several tens of cm above the floor surface, the LED
Check that 14 is lit. Next, the white paper is removed and the light quantity level is adjusted by the variable resistor VR ₂ . To do this, VR ₂ is once turned until the received light quantity comparator operation confirmation LED 15 is turned on, and then turned in the opposite direction to turn off. For confirmation, a black paper is placed on the floor so that the LED 15 is turned on when the amount of reflected light is reduced.

As shown in FIG. 5 (b), when a car enters a parking lot, if the ceiling of the car comes directly under the object detection device 21, the distance becomes short. Therefore, it is necessary to detect the presence of the car. You can By setting the diameter of the projected beam to about 10 cm, even when there is a vehicle in an oblique direction as shown in FIG. 5C, it can be determined that there is a vehicle based on both the distance and the light amount.

Although the present invention has been described with reference to a specific embodiment, the following modifications and applications are possible and are included in the scope of the present invention.

1) The light projecting portion may be a laser light emitting element without using a light projecting lens. (Because the light beam can be generated directly.)

2) The light receiving section may be another distance detecting element instead of the PSD.

3) In the above-mentioned embodiment, 50 because of the following reasons.
Although the intermittent operation for msec is performed and the values of the distance and the received light amount are processed by the average value, it may be continuous instead of intermittent. -To reduce power consumption. The on / off ratio is increased in order to increase the energizing current of the light emitting LED, so that there is a margin for the maximum rated power of the LED. -The calculation IC is an intermittent drive system.

4) If the object to be detected is one that absorbs light,
There is no reflected light and distance detection is not possible. In order to solve this problem, when the amount of received light is less than a certain value, the state is changed and a function of detecting and outputting is provided, but it may be used in combination with a method other than checking the amount of received light. The following method is also conceivable as a solution other than the received light amount check.・ Since it is rare that the whole object is absorbed,
Detects by measuring the distance at two or more parts.・ Use with other detection methods such as ultrasonic waves. (The main detection is a distance measurement method using light.)

5) Many sensors may be installed.
In this case, since the signal outputs are multiplexed and the signals are transmitted (collected) with a small number of signal lines, it is possible to use a circuit for multiplexing the signals by connecting the circuit inside or outside the sensor. It is also possible to provide a circuit having another function in the sensor.

6) Although infrared light is used in the above embodiment, other visible light or laser light may be used.

7) The object detected by this sensor is not limited to a car, but can be an object other than a car, a person, or a living thing. Further, the detected object can be detected even when it is stationary or moving.

8) It is also possible to install several sensors at the same location to detect the moving direction of the object and to determine the size of the object.

9) If the response speed is set to an appropriate value, it is possible to use the characteristic that an object having a fast passage speed is not sensed but a slow object is sensed.

10) When the detected object is small, the distance cannot be detected. By using this characteristic, it is possible to determine the size of the object.

In the embodiment, the distance information and the received light amount information are discriminated by the comparator and the coupling timer circuit provided in the sensor. However, the distance information and the received light amount information are processed by using a CPU or the like. It is also possible to perform effective discrimination processing. In this case, a processing circuit such as a CPU may be provided inside the sensor or outside the sensor. When a processing circuit is provided outside the sensor, the distance information and the received light amount information can be sent by serial communication to reduce the number of wires.

[0029]

As described above, according to the present invention, since the light beam is used, the detection area is narrow and the detection portion can be set accurately. Also, even if there is another object around the detector, it will not be affected unless the light beam is blocked,
Easy to install.

[Brief description of drawings]

FIG. 1 is a block diagram of an object detection device according to the present invention.

FIG. 2 is an explanatory diagram of an operation of the PSD used in the embodiment of the present invention.

FIG. 3 is an explanatory view of the principle of distance measurement using PSD.

FIG. 4 is a graph showing the relationship between the distance measured by PSD and the output current.

FIG. 5 is an explanatory diagram when the present invention is applied to detection of a car in a parking lot.

[Explanation of symbols]

1 intermittent oscillator, 2 timing control circuit, 3 LED
Drive circuit, 4 infrared LED, 5 light projecting lens, 6 light receiving lens, 7 PSD, 8 amplifier, 9 distance calculation circuit, 10 distance comparator, 11 light receiving amplification circuit, 12 light receiving amount comparator, 13 coupling / timer circuit, 14 LED for confirming operation of distance comparator, LE for confirming operation of 15 received light amount comparator
D, 21 Object detection device, 22 cars

Claims (2)

[Claims] 1. A light emitting unit and a light receiving unit, which are installed at a fixed interval, and the detection target object is controlled by an incident angle of reflected light from the detection target object emitted from the light projecting unit with respect to the light receiving unit. Object detection characterized by providing distance measuring means for measuring a distance, and detecting means for detecting the presence or passage of an object when the distance measured by the distance measuring means becomes shorter than the distance of the background apparatus. 2. The object detecting device according to claim 1, wherein the presence or the passage of an object is detected even when the level of the incident light on the light receiving section becomes lower than the level of the incident light on the background.