JPS5941142B2 - Vehicle speed detection method using photoelectric conversion elements - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A technology for detecting the speed of a vehicle traveling on a road as an electrical signal is an important basic technology in the field of traffic control and control for vehicles.

Conventionally, there have been methods for detecting the running speed of a car, such as a direct detection method based on physical phenomena such as the Doppler radar method, an indirect detection method based on the temporal occupancy rate of the vehicle detector such as ultrasonic waves or loops, or A method of detecting a vehicle based on the difference in passing time between two vehicle detectors arranged at a constant interval has been used.

However, all of these speed measuring devices have to be installed and used near the road, so installation and maintenance work is troublesome, and there are problems in terms of price.

The present invention solves these problems and simultaneously detects vehicle speeds at multiple points by installing a simple and inexpensive vehicle speed detection device at a relatively high location near the road.

Accordingly, in the present invention, a large number of photoelectric conversion elements are arranged along the lanes of the road image on the imaging plane of a single lens system, and thereby traffic information on a long road section can be transmitted at one speed. In addition to enabling detection by a measuring device, the structure is configured to prevent a decrease in reliability and maintainability due to weather effects when a large number of vehicle detectors are arranged along a road, and the image forming surface is A large number of photoelectric conversion element groups are arranged and installed with two photoelectric conversion elements as one detection unit, and in particular, the distance between the starting ends of the detection area on the road surface corresponding to the light receiving surfaces of these two photoelectric conversion elements is By setting the wavelength below the minimum spatial wavelength of the video signals generated from the photoelectric conversion elements and processing the electrical video signals from those photoelectric conversion elements with a simple electric circuit, it is possible to The feature is that it is possible to accurately detect the traveling speed of a car at each point.

To explain the present invention in more detail, FIG. 1 is a diagram showing its operating principle, in which two photoelectric conversion elements are detected along a lane 3 of a road whose image is formed on an image forming surface 2 of a lens system 1. A large number of photoelectric conversion element groups A1, B7, A2,
B2, ...... are arranged in an array, and from the photoelectric conversion element of one detection unit among these photoelectric conversion element groups,
Electrical video signals are generated depending on the shape, color, illumination condition, etc. of a car traveling on the road R, as illustrated in FIGS. 2A and 2B, respectively.

Here, the signal waveform of B occurs somewhat later than the signal waveform of A, and the delay time is determined by the speed of the motor vehicle, so both signal waveforms can be easily processed to detect the speed of the vehicle. can do. FIG. 3 shows an outline of a circuit for electrically processing the above-mentioned video signals. The video signals 1 of A' and B are amplified by amplifiers 4 and 5, and then applied to differentiating circuits 6 and 7. , a differential waveform that fluctuates around the zero level as shown in FIGS. 2C and 2D is vi-converted.

These differential waveforms are applied to the next-stage comparison circuits 8 and 9, and the waveforms above the zero level are shaped to a constant value, thereby obtaining the pulse waveforms shown in FIG. 2E and F. And E
The waveform of F is used as a set signal, and the waveform of F is used as a reset signal.
When applied to the set type flip-flop circuit 10 of FIG. 3, the pulse signal G of FIG. 2 can be obtained. This is a pulse signal having a time width that is inversely proportional to the traveling speed of the vehicle. In order to perform such a traveling speed detection operation reliably, certain conditions are required between the set signal and the set signal applied to the flip-flop circuit 10 of FIG. That is, after the first set signal is generated from comparison 2 circuit 8 in FIG. 3 and before the next set signal is generated, the NOSET signal must arrive from comparison circuit 9. Without this reset signal, the duration of the output pulse of the flip-flop circuit 10 would not be inversely proportional to the speed of the vehicle. In order to avoid such malfunctions, two detection areas formed on the road surface corresponding to the light receiving surfaces of photoelectric conversion elements A1 and Bl, A2 and B2 of one detection unit in FIG. At the same time, the distance between the starting edge of the first detection area and the starting edge of the next detection area in the direction of travel of the three lanes is determined by the distance between the starting edge of the first detection area and the starting edge of the next detection area. Must be set below the minimum spatial wavelength of the video signal. Here, the spatial wavelength means a spatial length corresponding to one cycle of brightness change distributed in the front-rear direction of the automobile. The value varies somewhat depending on the length of the detection area in the direction of travel, but is approximately 2 to 3 meters on the road surface. Another problem is that the reset signal is less likely to be generated than the set signal, and in this case, a pulse signal with an abnormally long time width may be generated.

In order to avoid such a phenomenon, by appropriately setting the circuit constants of the amplifier 5 in FIG. 3 that produces the reset signal, the differentiator circuit 7, and the comparator circuit 9, it is possible to make the reset signal higher than the set signal. Just make it easier to occur. Furthermore, the shape of each photoelectric conversion element in the present invention must be set so that it gradually becomes smaller at a rate determined by the focal length of the lens and the perspective drawing method. , a large number of photoelectric conversion element groups in which two photoelectric conversion elements are used as one detection unit can be manufactured at once.

As described above, according to the vehicle speed detection method of the present invention, vehicle speed can be detected using a simple and inexpensive speed detection device equipped with a group of photoelectric conversion elements and a simple electric circuit that processes its video signal. Moreover, one speed detection device can simultaneously detect vehicle speeds at multiple points.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the operation for vehicle speed detection in the present invention, Figures 2A-G are signal waveform diagrams in the process of processing the detected video signal, and Figure 3 is an overview of the processing circuit for the video signal. It is a block diagram. 1...lens system, 2...imaging surface, 3.
...Lane, 10...Flip-flop circuit.

Claims (1)

[Claims] 1 Along the lane of the road image imaged on the imaging plane of the lens system, a large number of photoelectric conversion element groups, each consisting of two photoelectric conversion elements as one detection unit, are arranged in an array to constitute each detection unit. The distance between the starting ends of the detection areas on the road surface corresponding to the light receiving surfaces of the two photoelectric conversion elements is set to be less than or equal to the minimum spatial wavelength of the video signal generated from the photoelectric conversion elements, and the first detection area of the detection unit is A flip-flop circuit that uses a signal from a corresponding photoelectric conversion element as a set signal and a signal from the other photoelectric conversion element as a reset signal converts the vehicle's running speed into the time width of a pulse signal and measures it. A vehicle speed detection method using a group of photoelectric conversion elements.