JPS5934185A - Optical type vehicle detector - Google Patents

Abstract

PURPOSE:To raise an S/N ratio and to decide exactly whether a vehicle exists or not, by using a laser diode of a pulse driving type as an illuminating light source, and using a photodetector such as a photodiode, etc., as a detector. CONSTITUTION:A laser diode 5 is driven by a driver 4 in accordance with turn- on and turn-off of a pulse train 3 from a pulse generator 2. The laser diode 5 oscillates in the time of turn-on of the pulse train 3, and its output light is irradiated toward a reflecting body 16 on a road as transmitting light 7 through a transmitting lens 6. Light reflected from the road surface including the reflecting body 16, out of the transmitting light 7 is received by a photodiode 10 through a receiving lens 9. In accordance with whether a vehicle 1 exists or not on the reflecting body 16, receiving light 8 which is subjected to strength and weakness variations of intensity of light is photoelectrically converted by the photodiode 10, is inputted as a receiving signal to a gate 12, and the gate 12 outputs a detecting signal 13. A deciding device 14 decides whether the vehicle 1 exists or not in accordance with amplitude of the detecting signal 13 is large or small.

Description

[Detailed Description of the Invention] This invention relates to the presence of vehicles on roads, etc. This invention relates to improvements in optical vehicle detectors.

On the road? Is all traffic control the means to detect all moving vehicles? It is the most basic and important information source for conducting research, and various types of this type have been used in the past, such as the loop coil method and the ultrasonic wave method. However, with the loop coil method, it is necessary to bury the loop coil in the road surface, and with the ultrasonic method, accurate measurements may not be possible due to the influence of reflections from surrounding objects or environmental changes such as temperature or wind. Ta. This invention was developed to overcome these drawbacks, and its features include a pulse-excited laser diode as the illumination light source and a photodetector such as a photodiode as the detector. The main feature is that the entire output of the photodetector is detected in synchronization with the excitation pulse of the laser diode, and the presence of a vehicle is completely detected based on the magnitude of the output.

The figure is a column diagram of one embodiment of this invention, and in figure 1 (
1) is a vehicle as an object to be measured, a pulse train (3
) full output pulse generator, +41tff, pulse train (
31 is input and this pulse train (3) is a driver that causes the laser diode (5) to fully oscillate only when it is on. Transmission lens for (81fl Received light reflected by the transmission source (7) from the vehicle (1), etc., +91
1c Received light (8) All photodiodes [1 (receiving lens for focusing on l, a] Received signal which is the output of IrI photodiode 00, t12rt Hals sequence (received signal only when 31 is on? As detection signal 0) game)
, [141H Determination unit consisting of a microcomputer, for example, which completely determines the presence or absence of a vehicle based on changes in the magnitude of the detection signal α3; 09 is a laser diode (5), and a transmission lens (6);
, a receiving lens (9), and a photodiode Qα, and this sensing head FI51μ is mounted from above the road toward the road surface VC. This tape is realized as a reflector.

The sending light (71 is almost evenly illuminated on the reflector tui,
Further, the field of view of the receiving lens (9) on the road is set to include the reflector aQ. In addition, it is assumed that the vehicle il+ in FIG. 9 travels in the direction of the arrow.

In this configuration, the laser diode (5) is driven by the driver (4) according to the on/off of the pulse train (3) from the pulse generator (2), and the pulse train (3) is driven by the driver (4).
) during the ON time of the laser diode (51) oscillates, and its output light is transmitted through the transmitting lens fil i- (7)
As a reflector a on the road, it is irradiated towards the road.
,,-10,000 receiving lens (9) full valve and photodiode aO
Of the transmitted light (7), the light reflected from the road surface including the reflector ab+2 is received. Since the reflector rm is white, it has a high reflectance. Therefore, the vehicle (
1), the intensity of the received light entering the photodiode +11 is strong, and conversely, when the vehicle fi+ is present on the reflector ae, the intensity of the receiving light entering the photodiode aG is weak. The received light (81rI photodiode (IG) photoelectrically converts it and enters the gate 021 as the received signal αυ, Gate 02'''c
Is the received signal only when the ta-pulse train (3) is on, that is, while the transmitted light (7) is output? It is output as the amplified detection signal aJ. Therefore, it is synchronized with the detection signal QIJ pulse train (3) and its amplitude corresponds to the intensity change of the received light (8). The determiner ■ determines whether the receiving lens (9
) determines whether there is a vehicle il+ within the field of view.

As explained above, if this invention is used, the illumination light [
7) Since the laser diode (5) is fully pulse driven, the forward light output of the transmitted light (7) is large, and the reflector αef is installed on the road surface, so the received light ( 8) The signal-to-noise ratio is adjusted by keeping the intensity constant, and it is possible to accurately determine the presence or absence of a vehicle. By adding a laser diode (51) to the optical filter 7 as an oscillation bandpass filter, it is possible to make it less susceptible to light such as sunlight.

In the example, a photodiode αω? is used as a photodetector.
I used an image sensor or 00D (cha
rge coupled device), etc.
By using the device 7 that detects the spatially distributed sound of 1, it is also possible to more accurately capture the entire position of the vehicle.

Furthermore, in the example, white tape was used as the reflector UE? However, it is also possible to apply the cat's eye or paint completely, or use the zebra mark used for crosswalks depending on the location.

Also in the example is a sensing head! Is' (jAlthough it was installed above the road, it can also be installed on the side of the road to capture the entire side of the vehicle (1).

[Brief explanation of the drawing]

The figure is a configuration diagram of an embodiment of the present invention, (11 is a vehicle, +2+H pulse generator 1411'; J driver, (5
) is a laser diode, t6N-J transmission lens, (9)
is the light receiving lens, Ll is the photodiode, and UARS gate. [141 is a judge, +151 is a sensing head, and ue is a reflector. Agent Makoto Kuzuno

Claims (1)

[Scope of Claims] An optical vehicle sensor installed above or to the side of a road and configured to detect the presence or absence of a vehicle on a grooved road using an illumination light source and a light receiver. A laser diode that oscillates with a pulse train as an illumination light source, a transmitting optical system that transmits the output light from the laser diode to the entire road, and all or part of the field of view of the transmitting optical system on the road. a receiving optical system, a reflector installed on the road surface and within the field of view of the transmitting optical system and the receiving optical system, and a transmission from the laser diode that is focused by the receiving optical system. A light receiver that receives all of the light, a gate that outputs the photoelectric conversion signal from the light receiver only when the laser diode is in oscillation operation based on the pulse train, and a determiner that completely determines the presence or absence of a vehicle from the output of the gate, and a full set of equipment; Only while the laser diode is oscillating, all the photoelectric conversion signals of the light receiver are outputted by the gate, and based on changes in the output from the gate, it is judged by the judge that a vehicle is present within the field of view of the receiving optical system.・An optical vehicle detector that is fully characterized by being able to make all judgments.