JP3447324B2 - Detector for dirt on translucent panel - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention covers a front surface of an optical element such as a vehicle collision prevention device using a laser beam and transmits emitted light and reflected light. The present invention relates to a dirt detection device for a translucent panel having: 2. Description of the Related Art A schematic structure of a conventional transmissive panel dirt detecting device of this type will be described with reference to FIGS. 3 and 4, taking a vehicle collision preventing device as an example. That is, in the figure,
Reference numeral 1 denotes a distance sensor for detecting a distance between a host vehicle (a vehicle to which the present apparatus is attached) and a preceding vehicle which is an obstacle in front by using a laser, and includes a light emitting unit 1a and a light receiving unit 1b. Reference numeral 1a denotes a laser diode driving unit 4, a condensing lens 5, and a laser diode (LD) 6 positioned at the focal point of the condensing lens 5 for emitting a laser beam in a pulsed manner at a predetermined period toward a vehicle ahead. The laser beam from the laser diode 6 is emitted through the condenser lens 5. The light receiving portion 1b selectively extracts light having a frequency of only a specific frequency component out of light from the front and allows the light to pass therethrough. The light receiving portion 1b collects light passing through the optical filter 7. A distance detecting photodiode (PD) 9 for receiving light collected by the Fresnel lens 8, a light receiving amplifier 10,
A distance counter 11 that starts counting a clock signal based on the start of supply of a timing signal from a gate timer 14 to be described later, and stops counting based on an output from the light receiving amplifier 10 to output a distance signal; 6, a dirt detection photodiode (PD) 12 arranged to receive a laser beam reflected by dirt on the transmission / reception window glass 16 and natural light such as sunlight from the outside, and this photodiode. A light transmitting / receiving window glass stain detection circuit 13 for detecting a stain degree of the light transmitting / receiving window glass 16 based on the detection output from the signal transmitting unit 12 and outputting to the signal converter 15 a stain degree indicating signal which changes according to the stain degree; For setting respective drive timings of the light receiving amplifier 10, the distance counter 11, and the laser diode drive unit 4. Gate timer 14 for outputting a signal
And a signal converter 15 that processes the dirt degree display signal from the distance counter 11 and the transmitting / receiving window glass dirt detecting circuit 13 and supplies the processed signal to the microcomputer 2 described later. A microcomputer 2 calculates the relative speed between the host vehicle and the preceding vehicle from the degree of change per unit time of the distance signal detected by the distance sensor 1, and smoothes the calculated relative speed. The process is performed at predetermined time intervals, and based on the detected distance R, the smoothed relative speed V, and the deceleration α of the vehicle based on a vehicle speed pulse signal from a vehicle speed sensor (not shown). It is determined whether or not there is a possibility of collision between the vehicle and the preceding vehicle. If it is determined that there is a possibility of collision, an alarm signal is output.
Further, the microcomputer 2 receives the diffuse reflection light due to the contamination of the window glass 16 for transmitting and receiving light from the laser diode 6 by the photodiode 12 shown in FIG. 7D
). The microcomputer 2 has an input / output interface 2a and an information processing section 2b as shown in FIG.
And the RAM 2c. Further, the light emitting section 1a and the light receiving section 1b are housed in a case having only one side opened, and after they are housed, the entire opening is made of a window glass (translucent panel) 16 for transmitting and receiving light. The laser beam from the laser diode 6 is emitted in a pulsed manner at a predetermined cycle through the transmission / reception window glass 16, and the reflected light from the vehicle ahead is reflected by the photodiode 9.
Is received by the Next, the transmitting / receiving window glass dirt detection circuit 1
3 will be described. That is, as shown in FIG. 6, the light transmitting / receiving window glass 16 is disposed on the same side with the laser diode 6 with respect to the transmitting / receiving window glass 16 and a part of the laser beam emitted from the laser diode 4. A photodiode 12 for receiving light reflected by dirt on the surface;
A DC cut filter that cuts off only a DC component due to natural light or the like in the detection output from the photodiode 12,
A peak hold circuit for detecting a peak hold value of an output signal corresponding to light reflected by the window glass 16 extracted by the DC cut filter, and outputting the voltage value as a stain degree display signal; When the output value exceeds a set reference value, it comprises a series circuit with a comparator for outputting a stain warning signal. Reference numeral 3 denotes an alarm generator which generates an alarm in response to a dirt alarm signal output from the microcomputer 2.
The alarm generator 3 includes: an alarm speaker 3a driven based on an alarm signal via an input / output interface 2a from an information processing unit 2b of the microcomputer 2;
A 7-segment display 3c for displaying a dirt degree display signal generated by the information processing unit 2b and supplied via the input / output interface 2a; an alarm volume setting and an alarm distance range (corresponding to the reference value of the comparator); And a setting switch 3d for performing the setting of “Yes”. Next, the operation of the above configuration will be described with reference to the flowchart shown in FIG. Normally, when the power is turned on, the microcomputer 2 proceeds to step ST100 and starts initialization. When the initial setting is completed, the laser diode 6 is intermittently driven by the laser diode driving unit 4 at a predetermined cycle, and the emitted laser beam passes through the condenser lens 5 and the transmitting / receiving window glass 16 in series, and Is reflected toward the vehicle, and if there is a vehicle ahead, the reflected light is received by the photodiode 9 via the transmission / reception window glass 16, the optical filter 7, and the Fresnel lens 8 in series, and the distance counter 11 Is supplied with a light receiving signal. The distance counter 11 counts clock pulses from the gate timer 14 during the period from when the laser diode driving section 4 is driven to when the light receiving signal is supplied, thereby detecting the distance between the host vehicle and the vehicle ahead. Is measured. The measured distance signal is transmitted to the signal converter 1
5, the input signal is supplied to the input / output interface 2a of the microcomputer 2, and in ST101, a distance signal is input to the information processing section 2a.
At 102, it is stored in the RAM 2c. Next, in ST103, the information processing section 2b compares the supplied latest distance signal with the previously obtained distance signal measured by the present apparatus a predetermined time before and stored in the RAM 2c, The amount of change in distance per unit time, that is, the relative speed V is calculated based on the comparison result, and the sequentially obtained relative speed V is smoothed in ST104 at every predetermined period Δt. Then, the smoothed relative velocity V for each time of a predetermined period Δt set in advance is set as a new relative velocity V. Thus, the risk of collision is determined in ST105. In this case, R is the inter-vehicle distance to the preceding vehicle (obstacle), V is the relative speed, and α is the deceleration of the own vehicle. When the inter-vehicle distance R reaches a value that satisfies Expression 1, and proceeds to ST106, it is determined that the own vehicle may collide with the preceding vehicle, and an alarm signal is supplied to the speaker 3a to generate an alarm, and The inter-vehicle distance R between the host vehicle and the preceding vehicle is displayed to inform the driver of the degree of danger, and the process proceeds to ST107. Also, when ST1 is not satisfied in ST105, the process proceeds to ST107. In step ST107, a window glass dirt display signal indicating the dirt on the window glass 16 for transmitting and receiving light is input, and whether or not the value is larger than a reference value is detected by the circuit 13 for detecting the dirt on the window glass for transmitting and receiving light. Judgment is made based on whether an alarm signal is output, and if it is larger, it is recorded in a non-volatile memory (not shown) in ST108. If it is determined in ST109 that this abnormal state is continued for n (sec), ST1
At 10, a dirt alarm signal is created and supplied to the display 3c, and the alarm content is displayed.
It returns to ST101. When it is determined in ST107 that the state is normal, and in ST109, the abnormal state is n (se
c) If it returns to the normal state without continuous operation, ST10
Return to 1. The window glass stain display signal is obtained as follows. That is, as shown in FIG. 6, the laser beam L emitted in a pulse form from the laser diode 6 is combined with the light beam A passing through the transmitting / receiving window glass 16 and the photodiode 1.
The light is reflected in two directions and is divided into a light ray C (a light amount increases in proportion to the degree of contamination of the transmission / reception window glass 16) received as a signal indicating the degree of contamination by the photodiode 12. Although the photodiode 12 receives natural light B such as sunlight, the pulsating voltage of the reflected light C is superimposed on the DC voltage of the natural light and output. In the superimposed signal, the DC voltage is cut off by the DC cut filter, and only the pulsating flow is extracted. The next-stage peak hold circuit peak-holds the pulsating signal, supplies the peak-held voltage value to the next-stage comparator, compares the voltage value with the reference value, and if the voltage exceeds the reference value, removes the contamination. It is output from the comparison circuit as an alarm signal. However, the above-described conventional translucent panel dirt detection device as described above is mounted on a vehicle collision warning device (at the front end of the vehicle, and is attached to the front of the vehicle.
When the vehicle is driven in a constant brightness environment such as in the daytime, for example, the photodiode 12 has natural light and reflected light. Since the combined light B with the light is received, a direct current component (natural light, as shown in FIG.
Some of which are repeated vary Tsu Kiwameteyu as DC voltage Q of the period T1 of the (A)) by the reflected light of pulsating (laser beam to Q) P is output after being superposed. When the vehicle is illuminated from the front for a short period of time by an oncoming vehicle, such as at night when traveling in a dark place, as shown in Q of the section T2 in FIG. A signal whose DC component fluctuates greatly is output, but only the DC voltage that changes very slowly is cut by the next-stage DC cut filter, and only the fluctuation is supplied to the next-stage peak hold circuit, and the peak hold is performed. to stain degree it is determined on the basis of only the output from the circuit, when illuminated from the front by headlight of the oncoming vehicle, during the short time T2, as advanced dirt degree, e.g. As shown in FIG. 7C, the peak-held voltage value exceeds the reference voltage. As a result, a dirt alarm signal is generated as shown in FIG. There is a problem that to become to become. Therefore, the present invention has been made in view of the above-mentioned problems, and ensures that even when the brightness of the environment in which the environment is used for a short time temporarily changes for a short time, the translucency is ensured. It is an object of the present invention to provide a device that can detect only the degree of contamination of a panel. According to the present invention, there is provided a dirt detecting apparatus for a translucent panel according to the present invention, wherein the light emitting means emits light in a pulsed manner to the translucent panel to which dirt can adhere. passing Tsu reflected light and the light-transmitting panel is reflected by the translucent panel
Light receiving means for receiving light and said light receiving means the reflected light
A corresponding pulse-like voltage waveform by the light-transmitting panel
Superimposed on the corresponding DC voltage by the light passing through and output,
And smoothing means for outputting the smoothed received light output from said light receiving means, a peak hold means for taking the peak value of the light-receiving output from said light receiving means, a differential taking the difference between the smoothing means and the peak holding means Means for outputting the output from the differential means as a stain degree display signal. According to the present invention, the output from the light receiving means for receiving the superimposed natural light whose brightness does not fluctuate or whose brightness changes very slowly and the reflected light which changes in a pulse shape is superimposed. A signal similar to the averaged signal is obtained by averaging on the one hand and peak holding on the other hand, and the difference between the two is taken, so that the brightness of the operating environment suddenly changes due to disturbance. Even in this case, only the DC signal components cancel each other, so that the signal indicating the degree of contamination is accurately extracted, and the reliability of the device can be improved. An embodiment according to the present invention will be described below with reference to FIG. In FIG. 1, reference numeral 20 denotes a light detection unit,
The photodiode (the photodiode 12 in FIG. 4)
20a) and a detection resistor 20b.
One end of the photodiode 20a is connected to the positive side of the power supply, and the other end is grounded to the ground via the resistor 20b. Reference numeral 21 denotes a signal A supplied from the photodetector 20.
A transistor 21a, resistors 21b and 21c, and a capacitor 21d. The collector terminal of the transistor 21a is on the positive side of the power supply, and the base terminal is the photodiode 20 of the photodetector 20.
The emitter terminal is connected to the connection point between a and the resistor 20b, and the emitter terminal is connected to the ground side via the resistor 21b. The emitter terminal is connected to the ground via a series circuit of the resistors 21c and 21d. Reference numeral 22 denotes a peak hold circuit, which comprises a transistor 22a, a capacitor 22b, and a resistor 22c. The collector terminal of the transistor 22a is connected to the positive side of the power supply, and the base terminal is connected to the photodiode 20a of the photodetector circuit 20. It is connected to a connection point with the resistor 20b. The emitter terminal is grounded via a capacitor 22b having one end grounded. Note that a resistor 22c is connected in parallel to the capacitor 22b. Reference numeral 23 denotes a subtraction circuit, and the smoothing circuit 21
Is connected to the minus input terminal of the subtraction circuit 23, the emitter terminal of the transistor 22a of the peak hold circuit 22 is connected to the plus input terminal, and signals supplied from both are connected. The difference between the magnitudes of B and C is calculated and output as a stain degree signal D. Reference numeral 24 denotes a comparator, which compares the degree-of-dirt signal D output from the subtraction circuit 23 with a set reference voltage, and when the output signal from the subtraction circuit 23 exceeds the reference voltage, a dirt warning signal ( 7D) is output. Next, the operation of the configuration shown in FIG. 1 will be described.
The photodiode 20a constantly detects the brightness of the measurement environment, passes a current corresponding to the brightness to the detection resistor 20b, and outputs a DC voltage (Q in section T1 in FIG. 2) or a slowly varying DC voltage (FIG. 2 in the T2 section, in this case, often at night or the like). Also, the photodiode 2
Numeral 0a receives a pulse-like reflected light beam, superimposes a corresponding pulse-like voltage waveform P on the DC voltage Q, and outputs a signal A as shown in FIG. This signal A is supplied to the next-stage smoothing circuit 21, and as shown in FIG. 2B, resistors 21b, 21c,
Since the waveform is smoothed by the time constant determined by the capacitor 21d and the pulse-shaped waveform is actually smaller than the DC voltage in terms of the effective value, a voltage waveform B close to the DC voltage waveform is output. The signal A generated at the detection resistor 20b is
The waveform is also supplied to the peak hold circuit 22 to obtain a waveform as shown in FIG. That is, when the transmission / reception window glass 16 is not dirty, the pulse waveform P is small,
Since the signal A is substantially constant, a waveform similar to the waveform of the DC voltage Q of the signal A output from the light detection unit 20 is output. For this purpose, the difference between the signal B obtained by the smoothing circuit 21 and the signal C obtained by the peak hold circuit 22 in the subtraction circuit 23 is obtained (FIG. 2D). ) Does not exceed the reference voltage of the comparator 24 at the next stage, and no dirt alarm signal is generated. However, as shown in section T3 of FIG. 2A, when the transmitting / receiving window glass 16 becomes dirty, the reflection by the window glass 16 increases, so that only the peak value of the pulse waveform due to the reflection is increased. (At this time, the DC voltage Q does not change), and the output voltage of the smoothing circuit 21 does not change from before, but the output voltage of the peak hold circuit 22 changes greatly. As a result, the subtraction circuit 23 The voltage value in the section T3 from becomes large,
The dirt warning signal E is output from the comparator 24. As described above , according to the present invention , even if the brightness of the measurement environment changes suddenly, the degree of dirt on the translucent panel can be reliably and accurately measured. An extremely effective effect is exhibited.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram of a circuit configuration for explaining an embodiment of an apparatus according to the present invention. FIG. 2 is an explanatory diagram of waveforms at various parts for explaining the operation of the embodiment shown in FIG. 1; FIG. 3 is a circuit block diagram for explaining an outline of a configuration of a conventional device. FIG. 4 is a detailed configuration diagram of a circuit block explanatory diagram of FIG. 3; FIG. 5 is a flowchart for explaining the operation of the microcomputer in FIG. 4; FIG. 6 is an explanatory view for explaining the relationship between the embodiment according to the present invention and a conventional example of a laser diode and a photodiode transmitting / receiving window glass. FIG. 7 is a circuit diagram of the light transmitting / receiving window glass stain detection circuit of FIG. 4; [Description of Signs] 1 Distance sensor 1a Light emitting unit 1b Light receiving unit 2 Microcomputer 3 Alarm generator 4 Laser diode driving unit 5 Condensing lens 6 Laser diode 10 Light receiving amplifier 11 Distance counter 9, 12 Photodiode 13 Transmitting and receiving window glass dirt Detection circuit 15 Signal converter 16 Window glass for transmitting and receiving light 20 Light receiving unit 21 Smoothing circuit 22 Peak hold circuit 23 Subtraction circuit 24 Comparator

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shigeru Nagago 1168 Suwa, Takatsu-ku, Kawasaki-shi Katakata (72) Inventor Hidefumi Ito 1-20-13 Himonya, Meguro-ku, Tokyo Himawariso 15 (72) Invention Person Takashi Yoshimura 1-11-20 Irie, Kanagawa-ku, Yokohama-shi, Kanagawa 104 (56) References JP-A-57-19625 (JP, A) JP-A-5-223937 (JP, A) JP-A-5-205 302887 (JP, A) Fully open 1987-135950 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 21/84-21/958 G01J 1/00-1/60 G01V 8/00-8/26

Claims (1)

(57) [Claim 1] Light emitting means for emitting light in a pulsed manner to a light-transmitting panel to which dirt can adhere, light reflected by the light-transmitting panel, and light transmitted from the light-transmitting panel. Light receiving means for receiving light passing through the optical panel, and the light receiving means corresponds by the reflected light
The light passing through the light-transmissive panel
Smoothing means for superimposing on and outputting the corresponding DC voltage, and smoothing and outputting the light receiving output from the light receiving means,
A peak hold means for peak-holding and outputting a light-receiving output from the light-receiving means, and a differential means for taking a difference between the smoothing means and the peak-hold means, and an output from the differential means indicating a degree of contamination. A translucent panel dirt detection device that outputs as a signal.