JPS6235159B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an optical traffic flow measurement device that includes an optical system that includes a lens that includes a required detection point on a road within its field of view and a light-receiving element that is placed on the imaging plane of this lens. The present invention relates to a device for detecting dirt on an optical system, particularly a lens.

An optical detection device having a light projector and a light receiver that receives light projected from the light projector,
The degree of dirt on the lenses of the light projector and light receiver can be detected from the relationship between the amount of light emitted and the amount of light received. However, since the optical traffic flow measurement device described above does not include a light projector, it is not possible to detect the dirt on the lens from the relationship between the amount of light emitted and the amount of light received. Even if there is no floodlight, if there is a reference light source, it is possible to detect dirt on the lens using the light projected from this light source as a reference, but on the road where the traffic flow measurement device is installed, There is usually no reference illumination source.

The present invention has been made in view of the above circumstances, and provides a detection device capable of detecting dirt on a lens without requiring a projector or a reference light projecting source.

The present invention relates to an optical traffic flow measuring device equipped with an optical system including a lens that includes a required detection point on a road within its field of view and a light receiving element disposed on the imaging plane of the lens. Means for determining that a vehicle is being detected based on the change; When it is determined that a vehicle is not being detected, the output signal level of the light receiving element is compared with a predetermined level, and when the level is below the predetermined level, a dirt detection time period is determined. Means for determining and storing this, means for detecting the peak level of the output signal of the light receiving element when it is determined that the vehicle is being detected when there is memory that it is the dirt detection time period, and the vehicle means for integrating the detected peak level for each detection until the number of detected vehicles reaches the required number; and comparing the peak level integrated value when the number of detected vehicles reaches the required number with a predetermined dirt determination value; The present invention is characterized in that it includes means for outputting a soiling detection signal when this integrated value is less than or equal to a soiling determination value.

In this invention, dirt in the optical system of a traffic flow measuring device is detected based on changes in the level of light received from the headlights of vehicles traveling on the road at night. That is, the level of the output signal of the light receiving element when a vehicle is not being detected represents the brightness or darkness of the road, and it is determined that it is nighttime when this output signal level is below a predetermined level. This is the dirt detection time period. Head of vehicle running at night
The light from the light serves as the above-mentioned reference light source for determining dirt on lenses and the like. Therefore, dirt detection can be accomplished very simply without the need for a special projector or reference light source. The amount of light from a vehicle's headlights varies depending on the type of vehicle, etc.
In this invention, the integrated value, that is, the average value, of the light reception level of the headlights is calculated, and since this average value is used as the basis, the influence of each vehicle is averaged out, and the error can be considered to be very small. can. The present invention can detect not only dirt on the lens but also deterioration of the light receiving element.

Hereinafter, the present invention will be described in which a plurality of detection points are set along the road at required intervals over a range of the required length of the road, and the vehicle at each of the detection points is placed in a position overlooking the above range. A case in which the present invention is applied to an optical traffic flow measuring device that includes an optical system including a plurality of light receiving elements for detection and that collects required traffic flow information based on output image signals of these light receiving elements will be described in detail. This traffic flow measurement device has 1
It is excellent in that it can collect traffic flow information from multiple points at a single location and is easy to install.

FIG. 1 shows how the camera of the traffic flow measuring device is installed. The camera 1 is placed at a required height position (for example, 6 m) above the road L using a support 3 or the like.
Required range in the length direction of road L (e.g. 100m)
It is set up to provide a bird's-eye view. Inside the camera 1, as shown in FIG. 4, an optical system 4 including a large number of light receiving elements and a lens 5 is provided. In this example, there are six detection points P1 within the field of view of camera 1.
~ There is P6. Pairs of light receiving elements dS1, dR1 to dS6, dR6 are arranged on the imaging plane of the optical system 4 in the camera 1 at locations corresponding to these detection points. These light receiving elements are composed of photo diodes, for example. As shown in Figure 2, each detection point (represented by P) has a set area S.
and a reset region R are set at a required interval l. A pair of light receiving elements (represented by dS, dR)
correspond to these regions S and R, respectively.

When the vehicle CA passes through the detection point P from the set area S to the reset area R, a vehicle detection signal (image signal) is output from the light receiving elements dS and dR by a time t, as shown in FIG. . Here, the rising edge of the output of each light receiving element dS, dR is detected, and the difference between the rising edges of both signals is defined as the detection time t. Since this detection time t is the time required for the vehicle to travel between the set area S and the reset area R (distance l), the traveling speed V of this vehicle is determined by the following equation. However, K is a constant.

V=K・l/t The distance that a vehicle actually moves during the detection time t is affected by vehicle color, vehicle height, etc. and varies slightly from vehicle to vehicle, and is actually not equal to the above distance l. do not have. However, by imagining a sensing surface at a position above the road surface by the required height, measuring the distance between both areas S and R on this sensing surface, and statistically correcting this distance, it is possible to increase the vehicle's running speed. It is possible to measure with high precision. The running speed of the vehicle is calculated not based on the time difference between the rises of the output signals of the light receiving elements dS and dR that detect the set region S and reset region R, but on the time difference when these rises reach a required level. Good too.

The processing device 2 performs various traffic flow information collection processes such as measuring the traveling speed of a running vehicle and detecting the degree of traffic congestion, as well as a process for detecting dirt on the lens 5, which will be described later. Referring to FIG. 4, the output signals of the light receiving elements dS and dR in the camera 1 are amplified by an amplifier 6 equipped with an automatic gain control function, and then amplified by a multiplexer 6.
The signal is sent to a channel device 7, where the outputs of each of the 12 light receiving elements are sequentially switched and sent to an A-D converter 8. The A-D converter 8 performs AD conversion on the output of the input light receiving element at a predetermined sampling period, and sends the result to the central processing unit (referred to as CPU) 1.
Send to 1. The CPU 11 measures the traveling speed using the method described above based on the data sent from the A-D converter 8, calculates other traffic flow information based on this traveling speed, and also calculates other traffic flow information such as the multiplexer channel device 7 and the A-D converter 8. Controls the D converter 8. The CPU 11 also executes a process for detecting dirt on the lens 5. The CPU 11 includes a data memory 12 that stores data for various processes, and a program memory (not shown) that stores execution programs thereof. The processing device 2 has a camera 1
A filter circuit and an amplifier are provided to remove low frequency components of signals input from the input signal, but illustration thereof is omitted for the sake of brevity.

FIG. 5 shows typical waveforms of vehicle detection signals during daytime and nighttime. In the daytime, the detection level of the road surface (referred to as road surface level) is relatively high, and the vehicle detection waveform is at a level higher than this road surface level and shows a waveform that corresponds to the shape and light reflectance of the vehicle.
Figure a). At night, the road surface level is low, and a waveform with a steep rise and high peak level appears (Figure 5b). This steeply rising waveform is due to the headlights of the vehicle.

Therefore, in the present invention, dirt on the lens 5 is detected based on the aging change in the average value of the peak level of the steeply rising waveform of the vehicle detection signal at night. The light from the vehicle headlights is
Although the amount of light varies depending on the type of vehicle, if the average value of vehicles running within a certain period of time or the required number of vehicles is taken, this average value can be considered to be approximately constant. Then, the lens 5 becomes dirty.
As the amount of light transmitted decreases, the average peak level of the signal due to the headlight light also decreases.
When the lens 5 is not dirty (for example, immediately after installing the camera 1), calculate in advance the average value of the peak level of the detection signal caused by the light from the headlight (this is set as the initial average peak level Q0). . Then, when inspecting for dirt, the average value of the peak level of the detection signal due to the light from the headlight (this is taken as the average peak level Q after aging) is similarly determined. These peak levels Q
Using 0 and Q, the transmittance A of the lens 5 is defined as follows.

A = Q / Q0 × 100 (%) When this transmittance A falls below a certain standard value AS, a warning is output as a semi-fouling state, and the semi-fouling state continues for a required period of time (for example, several days). It is determined that the lens 5 is soiled when the lens 5 is dirty, or when some of the six pairs of light receiving elements corresponding to the six detection points become semi-soiled. To determine whether the signal waveform is caused by headlights, a vehicle detection level L1 (Figure 5b) is set in advance near the midpoint between the average peak level and the road surface level, and when this level L is exceeded, a vehicle is detected. Signal. Also, as mentioned above,
Daytime and nighttime can be distinguished by the road surface level. This reference level for day/night determination is defined as nighttime determination level L2. This determination level L2 is set near the midpoint between the average value of the daytime road surface level and the average value of the nighttime road surface level (FIG. 5).

In order for the CPU 11 to execute the lens dirt determination process, the memory 12 stores an area used as a night flag F, an area used as a night time timer T, an area where the set time T0 is stored, a vehicle determination level L1, An area where the nighttime determination level L2 is stored, an area where the integrated value of the peak level is stored, an area where the number of sampling devices N is counted, an area where the number N0 of sampling devices required to obtain the average value of the peak level is stored. An area for storing the soil determination value LS is also provided. The soiling determination value LS is a value corresponding to the above-mentioned reference value AS.

FIG. 6 shows the procedure of lens dirt detection processing performed by the CPU 11. This process is executed by interrupting at regular intervals.
First, check whether the night flag F is on (step 21), and if the flag F is on, measure the night time (step 22), and if the flag F is off, clear the timer T (step 23). .

Next, check whether the detection time of the vehicle detection signal or the road surface level is being detected (Step 2).
4). The vehicle detection signal generally rises from the road surface level and indicates a level higher than the road surface level.
By setting a flag to remember that the signal rose above the road level, and erasing this memory when the signal returns to the road level, it is possible to determine whether a vehicle is being detected or the road level is being detected. can. If the road surface level is being detected, the road surface level is compared with the nighttime determination level L2 (step 27), and if the road surface level is below this determination level L2, it is determined that it is nighttime and the nighttime flag F is turned on. (step 28), the process ends. If the road surface level exceeds the determination level L2, the flag F is turned off (step 29) and the process ends.

If the vehicle is being detected in step 24, it is checked whether the content of the night time timer T has exceeded the set time T0 (step 25). The nighttime timer T starts counting time when the nighttime flag F turns on. Although it depends on the value of level L2, the nighttime flag F is generally turned on when it becomes dim, so even if the nighttime flag F is turned on, it will not be as dark as midnight for a while. The set time T0 is set to eliminate the dimly lit time period after the flag F2 is turned on. Therefore, if the contents of the timer T have not reached the set time T0, the process ends.

When the content of timer T exceeds the set time T0, it is checked whether it has reached the judgment level L1 (step 26), and if it is above this level L1, the peak level of the signal is detected and each The peak level is added for each interrupt and integrated (step 30). Then, the sampling number N is incremented by 1 (step 31), and it is checked whether the sampling number N has reached the required number N0 (step 32). When the required number N0 is reached,
Calculate the average peak level by dividing the integrated value obtained in step 30 by the required number of units N0 (step 3
3). Then, this average peak level is compared with the dirt judgment value LS (step 34), and if the average peak level is less than the judgment value LS, an alarm is issued (step 35), and the average peak level is equal to the judgment value LS. If it exceeds the threshold, the alarm is canceled (step 36). At step 26, the signal level becomes level L1.
If the sampling number N does not reach the required number N0 in step 32,
Finish processing.

FIG. 7 shows an example of a circuit that realizes dirt detection using a hardware configuration rather than a CPU. Output waveforms a to g of each of these circuits are shown in FIG. The vehicle determination circuit 41 performs processing substantially equivalent to step 24 described above, and when the output signal a of the amplifier 6 is a road surface detection signal, it sends the road surface signal to the day/night determination circuit 42, and in the case of vehicle detection. The vehicle detection signal is peak hold circuit 4.
5. Output to level determination circuit 46 and gate circuit 51. Further, after the vehicle detection signal falls and reaches the road surface level, a reset signal is output when a predetermined time T1 has elapsed while the road surface level is maintained. This certain period of time T1 is set in order to distinguish and measure vehicles one by one.

A nighttime determination level L2 is set in advance in the daytime/nighttime determination circuit 42, and a reset signal is output to the timer 43 when the input road surface signal is equal to or higher than this level L2 (during daytime determination). The timer 43 corresponds to the night time timer T described above, and
Time is measured by counting the input clock signals. Then, the set time T is reached without being reset by the output reset signal of the determination circuit 42.
When 0 has elapsed, a time-up signal b is output and sent to the logic determination circuit 44.

The peak hold circuit 45 holds the peak level of the vehicle detection signal until a reset signal is input from the determination circuit 41. The output signal c of this peak hold circuit 45 is transmitted to an attenuator 47
The signal is attenuated by 1/n and sent to the integration and hold circuit 48. This hold circuit 48
is for integrating the output of the attenuator 47 every time a sampling pulse, which will be described later, is input, and holding this integration result. This hold circuit 48
The output f is sent to the level determination circuit 49.

A dirt judgment value LS is set in advance in the level judgment circuit 49, and an output is generated when the integrated value output f of the hold circuit 48 is less than this judgment value LS. This output is sent to gate circuit 50.

The level determination circuit 46 has a vehicle determination level L1 set in advance, and outputs a vehicle determination signal d when the vehicle detection signal exceeds this level L1. This judgment signal d is sent to the logic judgment circuit 44. The logic determination circuit 44 identifies the time period for detecting dirt and counts the number of vehicles when it is determined that a vehicle is detected during this time period.
When the vehicle determination signal d is input while the time-up signal b is being input from the gate circuit 51, the control signal e is sent to the gate circuit 51. This signal e causes the gate 5 to
1 is opened and the vehicle detection signal is sent to the sampling pulse generation circuit 52, so that one pulse is generated from this circuit 52. This sampling pulse is sent to the above-mentioned integration hold circuit 48 and also to the sampling unit counter 53. This counter 53 has the required number N in advance.
0 is set, and when the count value reaches N0, an output is generated and the gate 50 is opened.

Therefore, when counting the required number N0 of vehicles, if the integrated value (signal f) has not reached the soiling judgment value LS, the output of the level judgment circuit 49 is outputted as the alarm signal g through the gate circuit 50. be done.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the installation status of the camera of the traffic flow measuring device, Figure 2 is an enlarged view of the detection point, Figure 3 is a waveform diagram showing the vehicle location signal, and Figure 4 is the inside of the camera and processing. The configuration and block diagram of the device; Figure 5 is a waveform diagram showing daytime and nighttime vehicle detection signals; Figure 6 is a CPU that performs dirt detection processing.
7 is a block diagram showing a dirt detection processing circuit, and FIG. 8 is a time chart showing output signal waveforms of each block in FIG. 7. DESCRIPTION OF SYMBOLS 1...Camera of traffic flow measurement device, 2...Processing device, 4...Optical system, 5...Lens, 41...Vehicle judgment circuit, 42...Day/night judgment circuit, 43...Timer, 44... Logic judgment circuit, 45...Peak
Hold circuit, 46...Level judgment circuit, 48...
... Integration, hold circuit, 49 ... Level judgment circuit, 50, 51 ... Gate circuit, 53 ... Sampling unit counter, dS1, dR1 to dS6, dR6
... Light receiving element, P1 to P6 ... Detection point, L1 ...
...Vehicle judgment level, N0...Required number.

Claims (1)

[Claims] 1. Optical traffic system comprising an optical system 4 including a lens 5 that includes a required detection point P on a road L within its field of view and light receiving elements dS and dR arranged on the imaging plane of the lens 5. In the current measuring device, means 41 determines that a vehicle is being detected based on a change in the output signal of the light receiving element, and when it is determined that the vehicle is not being detected, the output signal level of the light receiving element is set to a predetermined level L2. Means 42, 43 for comparing and determining that it is the dirt detection time zone when the level is below a predetermined level and storing this; when it is determined that the vehicle is being detected when there is a memory that it is the dirt detection time zone; means 4 for detecting the peak level of the output signal of the light receiving element;
5. For each vehicle detected, the number of detected vehicles is the required number N0
means 48 for integrating the detected peak level until the number of detected vehicles reaches the required number, and comparing the integrated value of the peak level with a predetermined dirt judgment value LS, and when the integrated value is less than or equal to the dirt judgment value. A dirt detection device in an optical traffic flow measuring device, comprising means 49 for outputting a dirt detection signal in the case of. 2. The dirt detection time period determination means determines whether the output signal level of the light receiving element has fallen below a predetermined level, and when a predetermined period of time has elapsed since the output signal level of the light receiving element has fallen below the predetermined level, the dirt detection time period has begun. A dirt detection device in an optical traffic flow measurement device according to claim 1, which determines and stores the determination.