JPH06102092A - Optical sensor - Google Patents

Abstract

PURPOSE:To automatically detect the contamination of a light projecting and detecting window without relying on visual observation. CONSTITUTION:A contamination detecting LED 32 is provided other than an actual light projecting LED 10 and both LEDs 10, 32 are driven in different timings. The back scattering light of the light emitted from the LED 10 due to an object is detected by a PD 12 to be outputted as an actual light detection signal. The reflected light of the light emitted from the LED 32 due to contamination 30 is detected by the PD 12 to be outputted as a contamination detection signal. The actual light detection signal and the contamination detection signal are obtained in different timings. A processing part compares the peak value of the actual light detection signal with that of the contamination detection signal in respective timings to detect a degree of contamination.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an optical sensor used in a scattered light receiving type optical measuring instrument or the like.

[0002]

2. Description of the Related Art Conventionally, a scattered light receiving type optical measuring instrument has been used for identifying rain, snow, fog and the like. In this type of application, light rays are projected into the atmosphere, and backscattered light from an object in the front (raindrops, snowflakes, water droplets of fog, etc.) is received, and the result is that the object in front is a raindrop. It is discriminating whether it is snowflakes or snowflakes.

FIG. 5 and FIG. 6 show the structure of a scattered light receiving type optical measuring device according to a conventional example. The device shown in these figures includes an LED 10 as a light projecting section and a PD 12 as a light receiving section. The LED 10 and the PD 12 are housed in a case 14, and the space between the LED 10 and the PD 12 is shielded by a light shield 16. A protective glass 18 is fitted on the front surface of the case 14, and the LED 10 allows the front object 20 (raindrop, raindrop, etc.) to pass through the protective glass 18.
The light beam is projected onto the snowflakes and the like, and the PD 12 receives the backscattered light from this object.

The LED 10 is driven by the drive signal supplied from the driver 22. When the LED 10 is driven by the driver 22 and the resulting light beam is projected on the object 20, the backscattered light is received by the PD 12, and the PD 12 photoelectrically converts the light. The light reception signal obtained as a result is amplified by the amplifier 24, converted into digital data by the A / D converter 26, and input to the processing unit 28. The processing unit 28 includes the A / D converter 26.
Based on the output of the above, processing such as determination relating to the object 20 existing in the front is executed, and the result is output to the outside. When this device constitutes a so-called telemeter system, the output of the processing unit 28 is transmitted wirelessly. It is also possible to output the processing result using a telephone line or the like.

[0005]

In such a structure in which the light projecting / receiving window formed of glass or the like is arranged on the front surfaces of the light projecting section and the light receiving section as described above, normal operation is caused by dirt such as dust attached to the light projecting / receiving window. Movement is hindered. For example, in the case of the configuration shown in FIG. 6, when a noticeable stain 30 is generated on the front surface of the protective glass 18, the stain 30 attenuates the light beam to be received by the PD 12, and it is not possible to perform appropriate light reception. . Therefore, in the conventional device, it is necessary to keep an eye on whether the light emitting / receiving window is dirty.

The present invention has been made to solve the above problems, and it is possible to automatically detect stains without visually determining the degree of stains. The purpose is to provide a device.

[0007]

In order to achieve such an object, the present invention provides a dirt detecting light projecting section for projecting a light beam forward at a timing different from that of the light projecting section, a light projecting section and a dirt. Means for separating the light receiving signal into a light receiving signal related to the light emitting unit and a light receiving signal related to the dirt detecting light emitting unit based on the light emitting timing of each of the detection light emitting units, and light emitting and receiving based on each separated light receiving signal. Means for determining the stain on the window.

[0008]

In the present invention, the light projecting section and the dirt detecting light projecting section are driven at different timings, and as a result, the light receiving signal related to the light projecting section and the light receiving signal related to the dirt detecting light projecting section are received as light receiving signals. And is obtained. The two are separated based on the light projecting timings of the light projecting section and the dirt detecting light projecting section, and the dirt of the light projecting / receiving window is determined based on each light reception signal obtained by the separation. Therefore, it is not necessary for a person to visually check the light emitting / receiving window for dirt, and it is possible to detect dirt more automatically.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. The same components as those of the conventional example shown in FIGS. 5 and 6 are designated by the same reference numerals and the description thereof will be omitted.

1 and 2 show the construction of an apparatus according to an embodiment of the present invention. The apparatus shown in these figures has a structure in which the dirt detection LED 32 and the peak hold circuit 34 are further provided in addition to the conventional apparatus shown in FIGS. The dirt detection LED 32 is housed in the shield 16 together with the PD 12. The peak hold circuit 34 is interposed between the amplifier 24 and the A / D converter 26 and reset by a reset signal from the driver 36. The processing unit 38 gives a mode switching command to the driver 36 in response to a command via a radio (telemeter) or a telephone line, and the driver 36 causes the actual light-emitting LED 10 or the dirt detection LED 32 to respond in accordance with this command. Drive selectively. Note that the processing unit 38 may issue a mode switching command in accordance with, for example, a built-in clock or the like, regardless of an external command.

The operation of this embodiment is shown in FIGS. 3 and 4.

When the actual light emission mode is set by the mode switching command from the processing unit 38, the driver 36
A drive signal (38 kHz) modulated by 5 pulses at 20 msc intervals is given to the LED 10 for actual light emission as a drive signal for actual light emission. Conversely, when the dirt detection mode is set by a command from the processing unit 38, the driver 36 gives a dirt detection drive signal to the dirt detection LED 32. As shown in FIGS. 3A and 3B, the drive signal for actual light projection and the drive signal for dirt detection are generated at different timings. Therefore, it is possible to separate the light reception signal based on this timing. it can.

FIG. 4 shows the signal waveform of each part in this embodiment. First, what is shown in FIG.
This is a modulation pulse used in the driver 36.
The driver 36 modulates a 38 kHz signal using this pulse, and supplies a signal having a waveform as shown in FIG. 4B to the actual light emitting LED 10 or the dirt detection LED 32 as a drive signal.

When a drive signal as shown in FIG. 4A is applied to the LED 10 for actual light emission, the light reception signal obtained from the PD 12 as a result is amplitude-modulated as shown in FIG. 4C. The waveform will be The processing unit 38 uses the received light signal, that is, the information such as the peak value of the actual received light signal or the like, to perform a process such as a predetermined determination. Therefore, the peak hold circuit 34 holds the peak value of the actual light reception signal amplified by the amplifier 24.

Further, the dirt detection LED 32 is shown in FIG.
When a drive signal as shown in (b) is given, the light reception signal (dirt detection signal) obtained from the PD 12 thereby has a waveform as shown in FIG. 4 (d). The peak of the dirt detection signal becomes smaller than the peak of the actual light receiving signal for the reason described later.

The driver 36 generates a reset signal in synchronization with the generation of the drive signal, and the peak hold circuit 34 is reset by this signal. Therefore, the peak value held in the peak hold circuit 34 is the peak value of the actual light receiving signal when the driver 36 is set to the actual light receiving mode, and the dirt value is set when the driver 36 is set to the dirt detecting mode. It is the peak value of the detection signal.
The processing unit 38 sequentially takes in the peak values held by the peak hold circuit 34 via the A / D converter 26, and determines the protection glass 1 from the difference between the peak values of the two.
The degree of stain of 8 is judged.

The peak value of the dirt detection signal is smaller than that of the actual received light signal because the former is reflected light and the latter is transmitted light. As shown in FIG. 2, dirt 3
If the LED 10 is driven in the state where 0 is generated in front of the PD 12, the light beam from the LED 10 is reflected by the object 20, passes through the dirt 30 and the like, and is received by the PD 12.
At this time, the dirt 30 scatters a part of the light beam, but most of the dirt is transmitted and reaches the PD 12. On the other hand, in the same situation LED3
If 2 is driven, most of the light beam from the LED 32 passes through the dirt 30 and is emitted to the outside, and a part, that is, the backscattered light by the dirt 30 is received by the PD 12.

Therefore, by comparing the peak values of the actual light reception signal and the dirt detection signal, it is possible to know how much the light ray is blocked by the dirt 30. For example, as the degree of dirt 30 is larger, the PD 12 associated with the LED 32 is
Since the light receiving level of is high, the difference between the peak values in FIGS. 4C and 4D is small. Therefore, the processing unit 38
The contents of the peak hold circuit 34 input via the / D converter 26 are successively compared, and when the difference between that in the actual light projecting mode and that in the dirt detection mode becomes small, it is determined that the protective glass 18 is dirty. The signal may be output by radio or telephone line.

As described above, according to this embodiment, it is possible to automatically detect the stain on the protective glass 18 without using any means such as visual inspection. Therefore, the ambiguity in the case of making the judgment by visual observation is eliminated, and the labor for visual inspection is reduced. In addition, since the frequency and the degree of occurrence of the dirt 30 can be collected as data, it is possible to predict and plan how often the cleaning of the protective glass 18 and the like should be performed. Become. As described above, in this embodiment, the maintenance efficiency is also improved.

In the above description, the LE for actual light projection is used.
The peak hold circuit 34 and the processing unit 38 separate the received light signal of D10 and the received light signal of the dirt detection LED 32. However, this separation may be performed by other means. In addition, an LED is used as a light projecting unit.
Although the PD is used as the light receiving unit, other types of elements may be used. In addition, the present invention is not limited to rain, snow, fog, etc., but can be applied to scattered light receiving type optical measuring instruments in general.

[0021]

As described above, according to the present invention,
A dirt detecting light emitting section that emits a light beam forward at a different timing from the light emitting section is provided, and the light receiving signal related to the light emitting section and the light receiving signal related to the dirt detecting light emitting section are separated based on the light emitting timing. Since the contamination of the light projecting / receiving window is determined by the above method, it is not necessary for a human to detect the contamination of the light projecting / receiving window by visual means. As a result, since automatic dirt detection is realized, labor related to visual inspection is unnecessary, and since ambiguity in visual judgment is eliminated, more accurate dirt detection can be performed. In addition, since the determination results can be aggregated, it becomes possible to perform maintenance such as cleaning of dirt while anticipating, and the maintenance efficiency is improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of an apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing a configuration near an LED and a PD in this embodiment.

FIG. 3 is a timing chart showing the operation of this embodiment, and FIG. 3A shows the drive signal for actual light projection,
(B) is a figure which shows the drive signal for dirt detection, respectively.

FIG. 4 is a waveform diagram showing the operation of this embodiment.
4A is a diagram showing a modulation pulse, FIG. 4B is a drive signal, FIG. 4C is an actual light receiving signal, and FIG. 4D is a dirt detection signal.

FIG. 5 is a block diagram showing a circuit configuration of an apparatus according to a conventional example.

FIG. 6 is a schematic cross-sectional view showing a configuration near an LED and a PD in this conventional example.

[Explanation of symbols]

 10 LED for Actual Projection 12 PD 18 Protective Glass 20 Objects such as Rain Drops and Snowflakes 30 Dirt 32 Dirt Detection LED 34 Peak Hold Circuit 36 Driver 38 Processing Section

Claims (1)

[Claims] 1. A light projecting unit for projecting a light beam forward, a light receiving unit for receiving backscattered light from an object in front and outputting a light receiving signal, and a glass or the like arranged in front of the light projecting unit and the light receiving unit. In a light sensor including a transparent light emitting / receiving window formed, a dirt detecting light emitting unit that emits a light beam forward at a different timing from the light emitting unit, and each of the light emitting unit and the dirt detecting light emitting unit. Means for separating the light receiving signal into a light receiving signal for the light emitting section and a light receiving signal for the dirt detecting light emitting section based on the light emitting timing, and a means for determining the dirt of the light emitting and receiving window based on each of the separated light receiving signals. An optical sensor comprising: