JPH07325997A - Optical vehicle sensor - Google Patents

Abstract

PURPOSE:To obtain the optical vehicle sensor which speedily detect a vehicle without sensing delay even when the vehicle already enters part of a sense area, and may be small in the electric power required to project light on the sense area. CONSTITUTION:Light emitting elements 1 are arranged in N columns in the travel direction of a road and in M rows in the crossing direction, and the sensor is equipped with a light emitting element driving circuit 13 which projects the light on projection surfaces in the sense areas sequentially on a partial charge basis by scanning alternate columns in the sense area in the travel direction of the road or scanning the area in the travel direction after scanning it in the crossing direction by the columns of the road, and a logic circuit 14 which receives the projection states of the respective columns and judges whether a sense output signal is continuous.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION This invention is installed on a road,
The present invention relates to an optical vehicle detector having a function of detecting the presence of a passing vehicle.

[0002]

2. Description of the Related Art FIG. 8 shows the installation of a conventional optical vehicle detector. In the figure, 21 is a light emitting / receiving unit, 22 is an attachment arm, 23 is a main body for processing signals from the light emitting / receiving unit, and 24 is a passing vehicle. FIG. 9 shows the configuration of the light emitting / receiving unit. In the figure, 1 is a light emitting element, 2 is a light emitting element current drive circuit, 3 is a light emitting element power supply, 4 is a condenser lens, 5 is a light receiving element, 6 is a light receiving current amplification circuit, 7 is a case of a light emitting and receiving section, 8 Is an optical window, 9 is a road surface level memory circuit, 1
Reference numeral 0 is a comparison circuit, 11 is a power supply device, 12 is a case of the main body, and 25a and 25b are interfaces for connecting the light projecting / receiving section 7 and the main body 12. FIG. 10 and FIG. 11 show the relationship between the light projecting range from the light projecting and receiving section and the sensing area. In the figure, a region of L ₁ × L ₂ on the road surface indicates a sensing area, and indicates a range in which the presence or passage of the target vehicle is detected and a sensing signal is output.

Next, the operation will be described. In FIG. 8, the light emitting / receiving unit 21 projects light onto the entire sensing area of the road surface to detect the intensity (level) of the reflected wave, and if the reflection level continues to be the same value, it is determined to be the road surface and stored. To do. When the vehicle enters the sensing area, the distance between the light emitting / receiving unit and the reflecting surface shortens and the reflection level increases, so the comparison circuit of the main unit determines that this is a vehicle and outputs a sensed signal to the host device. To do.

In FIG. 9, the interfaces 25a,
Power is supplied from the main body via 25b, and a high frequency pulse current is applied to the light emitting diode by the current drive circuit 2. The light emission power from the light emitting diode 1 is the optical window 8
It is irradiated to the road surface through. Light reflected from a road surface or a passing vehicle is collected by the light receiving element 5 by the condenser lens 4 through the optical window, amplified by the amplifier 6, and transmitted as a reflected light detection output signal to the main body via the interfaces 25a and 25b. . FIG. 12 shows the relationship between the change in the reflected light output due to the movement of the vehicle and the sensing output. As shown in the upper part of FIG. 12, the output signal of the amplifier 6 outputs the reflection from the road surface and maintains the low level state when no vehicle is present. This is stored in the storage circuit 9 as the road surface level, and a preset value is added to this road surface level to obtain the threshold level. When a vehicle enters the sensing area,
The reflected light detection output level increases and becomes a constant level when the entire vehicle enters the detection area. When the vehicle starts to leave the sensing area, the proportion of the reflected light from the road surface increases, and the light level decreases again toward the road surface level. In the comparison circuit on the main body side, the threshold level is set as shown by the alternate long and short dash line in the figure, and when the reflection level exceeds this threshold level, a sensing signal as shown in the lower part of FIG. 12 is output.

[0005]

As described above, the conventional optical vehicle detector detects the presence of a vehicle from the change in the reflection level by irradiating the entire sensing area with light all at once. Since the method is used, when a part of the vehicle is in the sensing area while the vehicle is entering or leaving the sensing area, the reflection level detected by the light receiving unit is
The reflection from the vehicle and the reflection from the road surface are superposed, and the time fluctuation of the detection level changes with the movement of the vehicle, so it has a certain inclination, which delays the detection or the area where the vehicle is completely detected. There is no sense output before going out of, and it becomes a non-sense state. Furthermore, there is a problem that the power required for projecting light in the sensing area becomes excessive.

The present invention has been made in order to solve the above problems, and promptly detects even a portion of a vehicle when it enters the sensing area, and does not promptly sense when the vehicle completely goes out of the sensing area. It is an object of the present invention to provide an optical vehicle detector that can be brought into a state and can save electric power required for light projection.

[0007]

An optical vehicle detector according to the present invention comprises a light emitting element drive circuit capable of sequentially emitting light by dividing an array of light emitting elements for emitting light onto a sensing area of a road surface in the traveling direction of a road. It is a thing.

Further, the invention is provided with a light emitting element drive circuit capable of sequentially emitting light by dividing the light emitting element array for projecting light onto the sensing area of the road surface in the transverse direction of the road.

[0009]

The optical vehicle detector constructed as described above is
Since the reflected wave for each scan is detected while scanning the light emitting area in the traveling direction of the road, there is no detection delay and the power required for light emission can be reduced.

Further, since the reflected wave for each scan is detected while scanning the light projecting area in the transverse direction of the road, there is no detection delay and the power required for light projecting can be reduced.

[0011]

【Example】

Example 1. FIG. 1 is a block diagram showing an embodiment of the present invention. The light emitting / receiving sections 1 to 8 and 25a are the same as those of the conventional device, and 13 is a light emitting element drive circuit. 9 to 12 and 25b of the main body are the same as those of the conventional device.
Reference numeral 4 is a logic circuit that determines the continuation of the sensing output signal in response to the light emitting state of each column.

In the optical vehicle detector constructed as described above, the light emitting element drive circuit 13 causes the light emitting element drive circuit 13 to drive the vehicle in the N direction in the traveling direction of the road.
Light is projected for each (sensing area) / N on the divided area (N is an integer of 4 or more), and the reflected light is detected. For example, with respect to the example of N = 6, FIGS. 2 to 4 show the relationship between the change of the reflected light and the sensed output signal with respect to the movement of the vehicle. As shown in the figure, the light is projected from the first column to the sixth column by energizing it in a short pulse for each column and then returning to the first column. The time for one cycle is several ms, and the operation flow is shown in FIG. For example, when the vehicle enters the light emitting area of the first row, when the reflection level rises at the _first light emitting (step S ₁ ) and the sensing signal is output (step Y ₂ ) exceeding the preset threshold level, second or subsequent column of light projection (step S ₂₎
The sensing output by is forced to the sensing state. Projecting step S of the Nth row when the vehicle tries to pass the sensing area
Even if only _N is detected, the sensing output by the next light projection of the first row is forcibly set to the sensing state until the detection of the vehicle from all rows disappears. If the vehicle cannot be sensed even when the light is projected up to the Nth row, a non-sensing signal is output (step Y ₁ ). When part of the vehicle enters the sensing area when the vehicle tries to enter or pass through the sensing area, the conventional method of projecting light to the sensing area at the same time is divided into the amount of reflected light from the vehicle and that from the road surface. The ratio of S is S / (L ₁ × L ₂ ) if only a partial area S of the vehicle is in the sensing area, but S / {(L ₁ / N) in the case of the N division method according to the present invention. × L ₂ } = N × S /
(L ₁ × L ₂ ), the area ratio of the vehicle to the road is larger by N times than that of the conventional method, and there is an advantage that the vehicle can be easily found from the reflection level. Also, the rising of the reflected light when the vehicle enters the sensing area is N times faster. Figure 6
Shows an example of the operation waveform.

Example 2. In the first embodiment, the method of sequentially projecting light for each column is used, but M division is also performed in the cross direction of the road, that is, the row direction of the light emitting element array, within the range where the sensitivity of the sensing system is realized.
A light emitting element current driving circuit for sequentially projecting light from the edge and scanning the sensing area is provided.

[0014]

As described above, according to the present invention, the sensing area is scanned into N divisions, and the reflected wave is detected for each scan. Therefore, the delay in vehicle detection is reduced and the projection power is reduced. It is 1 / N compared to the all area simultaneous projection method, and the device can be downsized.

Further, since the sensing area is scanned into M divisions and the reflected wave is detected for each scan, the delay in vehicle detection is reduced and the projection power is 1 compared to the all area simultaneous projection method. / M and the device can be miniaturized.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing a first embodiment of the present invention.

FIG. 2 is an operation explanatory diagram of the first embodiment of the present invention.

FIG. 3 is an operation explanatory diagram of the first embodiment of the present invention.

FIG. 4 is an operation explanatory diagram of the first embodiment of the present invention.

FIG. 5 is a flowchart showing the operation of the first embodiment of the present invention.

FIG. 6 is a waveform chart of each part showing the operation of the first embodiment of the present invention.

FIG. 7 is a waveform chart of each part showing the operation of the first embodiment of the present invention.

FIG. 8 is a view showing an installation situation of a conventional optical vehicle detector.

FIG. 9 is a circuit configuration diagram showing a conventional optical vehicle detector.

FIG. 10 is a diagram showing a sensing area of a conventional optical vehicle detector.

FIG. 11 is a diagram showing a sensing area of a conventional optical vehicle detector.

FIG. 12 is a diagram showing an operation of a conventional optical vehicle detector.

[Explanation of symbols]

 1 Light-Emitting Element 2 Current-Amplifying Circuit for Light-Emitting Element 3 Light-Emitting Element Power Supply 4 Condensing Lens 5 Light-Receiving Element 6 Light-Receiving Current Amplifying Circuit 7 Emitter / Receiver Case 8 Optical Window 9 Road Surface Level Storage Circuit 10 Comparison Circuit 11 Power Supply Device 12 Main Source 13 Light Emission Element drive circuit 14 Logic circuit

Claims (2)

[Claims] 1. The light-emitting elements are arranged in N rows (N is an integer of 4 or more) in the traveling direction of the road, and the light-emitting elements for each row sequentially project light in the road in the road to detect the area. A light emitting element drive circuit that can scan in the traveling direction of the road, and even when one row of light is projected from each row, if the reflected light exceeds the road surface level, a sensitive signal is output during one cycle of scanning. An optical vehicle detector having a logic circuit for outputting. 2. The light emitting elements are arranged in M rows (M is an integer of 4 or more) in the transverse direction of the road, the first column, the 1st row to the Mth row are sequentially projected, and the same is done from the 1st row of the next column. And the light emitting element drive circuit that can sequentially project light and scan the sensing area in the traveling direction of the road, and even if there is only one group at the time of projecting each row, if the reflected light exceeds the road surface level An optical vehicle detector comprising a logic circuit that outputs a sensed signal during one cycle of scanning including.