JPH0634372U - Dew condensation detector for camera case - Google Patents

Abstract

(57) [Abstract] [Purpose] Windshield 5 in camera case 41
When dew condensation occurs on 1, the dew condensation is accurately detected. An optical sensor 17 is provided so as to face the windshield at a position where the irradiation light of the light source 11 is reflected by a glass surface, and thus the irradiation light from the light source 11 detects diffused reflection light reflected by the windshield 51. The optical sensor 17 is provided with a timing pulse generation circuit 21 for blinking the light source 11, and the output terminal of the optical sensor 17 is provided with two sampling hold circuits 25 via a bandpass filter 23.
27 to connect the sampling and holding circuits 25 and 27.
Holds the optical sensor output value when the light source 11 is turned on and the optical sensor output value when the light source 11 is turned off, according to the timing signal from the timing pulse generation circuit 21, and the voltage comparison means 3
1 is used to detect the difference between both sampling and holding values.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a surveillance camera case, and more particularly, to a device for detecting the occurrence of fog such as dew condensation on a windshield provided in front of a camera in a surveillance camera case.

[0002]

[Prior art]

 Today, surveillance cameras for monitors are used for various purposes in many places and are used not only indoors but also outdoors. In such a surveillance camera used outdoors or a special purpose surveillance camera indoors, in order to protect the TV camera from dust, wind, rain, high temperature and humidity, a box shape with a glass window in front of the TV camera is used. May be stored in a protective case.

In the surveillance TV camera housed in the protective case, condensation may occur on the glass surface of the camera case or other places due to changes in temperature and humidity such as a sudden change in weather. If the glass surface becomes cloudy due to dew condensation, it may be difficult to monitor with the TV camera. Therefore, it has been attempted to attach a heater to the front glass and control the heater using a dew condensation sensor or a temperature sensor as a dew condensation removing means when dew condensation occurs on the glass surface.

As shown in FIG. 9, a method of automatically preventing and erasing dew condensation is to attach a dew condensation sensor 57 or a temperature sensor to a position outside the visual field of the monitor camera, such as a corner of the windshield 51, and As shown in FIG. 10, the sensor drive circuit 58 outputs a detection signal according to the relative temperature and humidity conditions detected by the sensor 57, and the value of this detection signal and the reference voltage output from the reference voltage generator 37 Are compared by the comparator 35, and when the value of the detection signal output from the sensor drive circuit 58 becomes equal to or more than a certain value or less than a certain value, the switch circuit 55 is turned on to heat the heater 53 attached to the windshield 51. I am going to do it.

[0005]

[Problems to be solved by the device]

 The dew condensation sensor used to prevent the above dew condensation is installed in the corner of the windshield or around it so as not to obstruct the field of view of the TV camera, but if dew condensation occurs on the windshield, it will cloud from the center of the glass. Condensation often begins to occur on the windshield, and even if the image on the monitor camera becomes unclear due to condensation on the windshield located in front of the camera lens, the condensation sensor does not detect fog and the heater does not work. There was a drawback that occurred.

In the prevention of dew condensation using the temperature sensor, dew condensation does not always occur due to a rapid change in temperature, and the temperature sensor does not always correctly detect the occurrence of dew condensation. In addition, there is a defect that it does not operate even if dew condensation occurs due to a rapid change in humidity. In order to eliminate such drawbacks, the present invention provides a detection device for detecting dew condensation on the windshield accurately and promptly.

[0007]

[Means for Solving the Problems]

 In the present invention, the incident angle of the light emitted from the light source with respect to the glass surface is increased, and the light receiving axis of the optical sensor is provided close to the glass surface perpendicular to the glass surface. The light source and the light sensor are provided toward the windshield in front of the camera lens so that the light sensor detects the light diffusely reflected by, and the timing pulse generation circuit that outputs the lighting pulse signal that blinks the light source at a constant cycle is provided. The timing pulse generating circuit outputs a first sampling pulse when the lighting pulse signal is at the H level and a second sampling pulse when the lighting pulse signal is at the L level, and outputs the output of the optical sensor as the lighting pulse. The first sampling pulse controlled by the first sampling pulse is passed through a bandpass filter having a passband matched to the frequency of the signal. Holds the output value of the optical sensor that has passed through the bandpass filter in the second sampling hold circuit controlled by the second sampling pulse and the second sampling pulse, and the difference between the holding values of both sampling and holding circuits exceeds the predetermined value. A voltage comparison means for outputting an ON signal is provided.

There is a case where a vertical sync signal is extracted from a video signal of a television camera by using a sync separation circuit and a lighting pulse signal output from a timing pulse generation circuit is synchronized with a vertical sync signal of the camera. Although the light source is installed so that the incident angle is large with respect to the glass surface, a signal component due to the lighting light of the light source is extracted from the video signal of the TV camera by a bandpass filter without providing an optical sensor, and the timing pulse generation circuit In some cases, the value of the video signal passed through the bandpass filter by the first sampling pulse and the second sampling pulse from is held by the sampling hold circuit, and the held values of both sampling hold circuits are compared by the voltage comparison means. .

[0009]

[Work]

 In the present invention, since the incident angle of the light emitted from the light source is increased, the reflection angle of the specularly reflected light from the windshield is also increased, and the light receiving axis of the optical sensor is reflected by providing it near the glass surface. Since the light is out of the position, if the windshield is transparent, the optical sensor does not detect the light emitted from the light source that is reflected by the glass surface.

Since the optical axis of the optical sensor is directed toward the windshield, when the glass is fogged and the light from the light source is irregularly reflected, the irregularly reflected light can be sensed by the optical sensor. In addition, since the irregularly reflected light from the light source sensed by the optical sensor is the lighting light having a predetermined period, it is easy to distinguish it from the natural light incident through the glass.

Further, since the first sampling and holding circuit holds the value of the signal that has passed through the bandpass filter by the first sampling pulse output when the lighting pulse signal is at the H level, the diffuse reflection light when the light source is lighting is held. The second sampling and holding circuit can store the received light amount of the optical sensor when the light source is not lit by the second sampling pulse.

[0012]

【Example】

 As shown in FIG. 2, the dew condensation detecting device for a camera case according to the present invention detects a fogging of a front glass 51 arranged in front of a camera in a camera case 41 accommodating a television camera 61, and a light emitting diode. The light source 11 using 12 or the like illuminates the windshield 51 with light.

When the light is emitted from the light source 11, as shown in FIG. 2, the light emitting diode 12 is arranged as the light source 11 in the vicinity of the windshield 51, and the incident angle of the light emitted from the light emitting diode 12 with respect to the windshield 51. While increasing α, the light source 11 illuminates the windshield 51 around the lens front position of the TV camera 61, and the optical sensor 17 is separated from the windshield 51 so that the light receiving axis is perpendicular to the windshield 51. As a result, the light from the light source 11 is prevented from being directly input to the optical sensor 17, and the reflected light reflected from the windshield 51 is not directly input to the optical sensor 17.

The light source 11 is arranged near the windshield 51 on the bottom plate 43 or the top plate 45 of the camera case 41, and the light from the light emitting diode 12 illuminates the front position of the camera lens on the windshield 51. The light-receiving axis is attached to the side plate 47 of the camera case 41 while aligning the light-receiving axis with the front position of the camera lens on the front glass 51, and the light-receiving axis of the light sensor 11 and the light-receiving axis of the light sensor 11 are shifted by about 90 degrees. In some cases, the direct light from the light source 11 and the reflected light from the windshield 51 may not be received. Therefore, as the light source 11, a shielding plate 16 is appropriately provided so that the light from the light emitting diode 12 is directed in an excessive direction. Do not diffuse it, and attach a light absorbing plate 19 etc. to the inner surface of the camera case near the optical sensor 17. Sometimes.

An example of a circuit for turning on the light emitting diode 12 of the light source 11 and processing the detection signal of the optical sensor 17 is the lighting pulse signal from the timing pulse generating circuit 21 as shown in FIG. In addition to the switching transistor 13 arranged in series with the light emitting diode 12, a light source 11 for lighting the light emitting diode 12 is used. From this timing pulse generation circuit 21, as shown in FIG. 1 is output as a lighting pulse signal, and the B signal is the first sampling pulse of the H pulse with the same frequency as the lighting pulse signal and delayed by 1/4, and the C signal. Shall output the second sampling pulse of the H pulse that has the same frequency as the lighting pulse signal and has a cycle delayed by 3/4. ing.

Therefore, in the light source 11 whose lighting is controlled by the lighting pulse signal, when the lighting pulse signal is at the H level, the switching transistor 13 becomes conductive and the power supply voltage is applied to the light emitting diode 12 through the protection resistor 15. When the lighting pulse signal is at L level, it is turned off and blinking lighting is performed for a certain period. The output terminal of the optical sensor 17 for receiving the light in which the light from the light source 11 is diffusely reflected and the external light is connected to the data input terminal of the first sampling and holding circuit 25 and the second sampling and holding circuit via the bandpass filter 23. Connected to the data input terminal 27 and timing the control terminal of the first sampling and holding circuit 25 so that the first sampling pulse from the timing pulse generating circuit 21 is input to the control terminal of the first sampling and holding circuit 25. The control terminal of the second sampling and holding circuit 27 is connected to the timing pulse generating circuit 21 so as to input the second sampling pulse to the control terminal of the second sampling and holding circuit 27.

As the band pass filter 23, a filter having a pass band at the frequency of the lighting pulse signal output from the timing pulse generation circuit 21 is used. As shown in FIG. 3, the optical sensor 17 has a windshield. When the natural light passing through 51 is detected, almost all of the D signal output from the optical sensor 17 is cut off, and the natural light and the diffused reflected light due to the blinking light from the light source 11 are input to the optical sensor 17. Among the D signals from the optical sensor 17, the illuminance change component due to the blinking light is passed through to the E signal.

Then, the first sampling and holding circuit 25 uses the first sampling pulse delayed by a quarter cycle from the lighting pulse signal, that is, the first sampling pulse output when the lighting pulse signal is at the H level to perform band pass. Since the output signal value of the optical sensor 17 that has passed through the filter 23 is held, the illuminance by the remaining natural light removed by the bandpass filter 23 and the light from the light source 11 are irregularly reflected and input to the optical sensor 17. By holding the output value of the optical sensor 17 according to the sum of the illuminance, the second sampling and holding circuit 27 causes the second sampling pulse delayed by three quarter cycles from the lighting pulse signal, that is, the lighting pulse. The optical sensor 17 that has passed through the bandpass filter 23 by the second sampling pulse output when the signal is at the L level Since the output signal value of 1 is held, the value of the illuminance due to the remaining natural light removed by the bandpass filter 23 is held.

Then, the voltage comparing means 31 to which the output signal of the first sampling and holding circuit 25 and the output signal of the second sampling and holding circuit 27 are input, the two input terminals of the operational amplifier 33 are respectively connected to the first sampling and holding circuit. 25 is connected to the output terminal of the second sampling and holding circuit 27 to amplify the difference between the output signal value of the first sampling and holding circuit 25 and the output signal value of the second sampling and holding circuit 27. The output terminal of the operational amplifier 33 is connected to one input terminal of the comparator 35 so that the difference signal is input to the comparator 35, and the reference voltage from the reference voltage generator 37 is connected to the other input terminal of the comparator 35. It is something to enter.

Therefore, when the value of the difference signal from the operation amplifier 33 exceeds the reference voltage, the comparator 35 has a large difference between the hold value of the first sampling and holding circuit 25 and the hold value of the second sampling and holding circuit 27. When, in other words, a large amount of irregularly reflected light due to the irradiation light from the light source 11 is received by the optical sensor 17, the H level ON signal is output from the voltage comparison means 31.

As described above, in the dew condensation detecting device 10 according to the present embodiment, the blinking light from the light source 11 is diffusely reflected by the front glass 51 by the optical sensor 17, and the light emitting diode 12 used for the light source 11 is detected. The amount of light received by the optical sensor 17 when the light is turned on is stored in the first sampling hold circuit 25, and the amount of light received by the optical sensor 17 when the light source 11 is turned off is stored in the second sampling hold circuit 27. The diffused reflection amount is detected by the difference between the two, and an ON signal is output when it exceeds a predetermined value. Therefore, when the diffused reflection amount of the windshield 51, that is, when fogging such as dew condensation or dirt occurs, this fogging is immediately detected. As shown in FIG. 4, the output terminal of the voltage comparison unit 31 is connected to the control terminal of the switch circuit 55, and the switch circuit 55 is attached to the windshield 51. If the switch circuit 55 is electrically connected in response to an ON signal while being in series with, the heater 53 can be immediately energized to eliminate the condensation when the windshield 51 becomes fogged.

As shown in FIG. 5, an auxiliary sampling and holding circuit 29 is inserted between the first sampling and holding circuit 25 and the voltage comparison means 31, and the auxiliary sampling and holding circuit 29 has a control terminal The sampling timing of the auxiliary sampling and holding circuit 29 may be synchronized with the second sampling and holding circuit 27 by inputting two sampling pulses.

In the second embodiment, the sampling timing of the first sampling and holding circuit 25 and the sampling timing of the second sampling and holding circuit 27 are changed when the illuminance of natural light changes greatly during the half cycle of the lighting pulse signal. It is possible to prevent erroneous operation due to displacement. Further, in order to prevent the lighting light of the light source 11 from being irregularly reflected and the irregular reflection light being input to the television camera 61 and causing flicker in brightness on the monitor screen, the light source 11 emits light in an invisible region such as infrared rays. When the diode 12 is used and a sensor having a frequency characteristic sensitive to the output wavelength band of the light source 11 is used as the optical sensor 17, the frequency of the lighting pulse signal may be an integral multiple of the vertical synchronizing frequency of the video signal. .

When irradiating the windshield 51 with invisible light in this way, the optical sensor 17 can detect diffused reflected light, but the TV camera 61 cannot catch the reflected light and can prevent flickering on the monitor screen. If the blinking speed of the light source 11 is set to be a multiple of the frequency of the vertical synchronizing signal, the light emitting diode 12 of the light source 11 is turned on faster than the human identification speed and the blinking frequency is a multiple of the synchronizing signal. Even if flashes, the brightness in each field is kept constant and no flicker occurs on the monitor screen.

As an example of surely adjusting the frequency of the lighting pulse signal to an integral multiple of the frequency of the synchronization signal, as shown in FIG. 6, the video signal of the television camera 61 housed in the camera case 41 is set. A vertical synchronizing signal is extracted from the vertical synchronizing signal by the vertical synchronizing separation circuit 63, and the extracted vertical synchronizing signal is input to the timing pulse generating circuit 21 as a trigger, and as shown in FIG. There is a method in which a lighting pulse signal is output, a first sampling timing signal is output when the lighting pulse signal is at H level, and a second sampling timing signal is output when the lighting pulse signal is at L level.

As another embodiment of the present invention, although the light source 11 is blinked by the lighting pulse signal from the timing pulse generating circuit 21 as in the above embodiment, the optical sensor 17 is omitted and the configuration is shown in FIG. Similarly, the video signal output terminal of the video camera 61 is connected to the bandpass filter 23, and the value of the video signal passed through the bandpass filter 23 is held by the first sampling hold circuit 25 and the second sampling hold circuit 27. For example, the auxiliary sampling and holding circuit 29 may match the input timing to the voltage comparing means 31 with the second sampling and holding circuit 27, and output the ON signal when a difference occurs in the hold values. Needless to say, the hold value can be directly input from the first sampling and holding circuit 25 to the voltage comparison means 31.

[0027]

[Effect of device]

 The present invention provides an optical sensor facing the front glass at a position where the light reflected by the windshield from the light source does not enter, and the light sensor detects irregularly reflected light by the front glass while blinking the light source at a predetermined cycle. This is a camera case dew condensation detector that detects the amount of diffused reflection by detecting the amount of diffused reflection from the difference in the amount of light received when the light is turned on and when it is illuminated. It is a detection device that can.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit example of a dew condensation detecting device according to the present invention.

FIG. 2 is a view showing a mounting example of a light source and an optical sensor in the dew condensation detecting device according to the present invention.

FIG. 3 is a time chart diagram showing each signal waveform in the dew condensation detecting device according to the present invention.

FIG. 4 is a circuit diagram showing an example of use of the dew condensation detecting device according to the present invention.

FIG. 5 is a block diagram showing a second embodiment of the dew condensation detecting device according to the present invention.

FIG. 6 is a block diagram showing a third embodiment of the dew condensation detecting device according to the present invention.

FIG. 7 is a time chart diagram showing each signal waveform in the third embodiment.

FIG. 8 is a block diagram showing a fourth embodiment of the dew condensation detecting device according to the present invention.

FIG. 9 is a diagram showing a mounting example of a conventional condensation sensor.

FIG. 10 is a block diagram showing an example of a conventional condensation prevention circuit.

[Explanation of symbols]

10 Condensation Detection Device 11 Light Source 17 Optical Sensor 21 Timing Pulse Generation Circuit 25 First Sampling Hold Circuit 27 Second Sampling Hold Circuit 31 Voltage Comparison Means 41 Camera Case 43 Camera Case Upper Plate 45 Camera Case Lower Plate 47 Camera Case Side Plate 51 Front Glass 53 Heater 55 Switch Circuit 57 Condensation Sensor 58 Sensor Drive Unit

Claims (3)

[Scope of utility model registration request] 1. A first pulse is output when a lighting pulse signal is output at a constant frequency and the lighting pulse signal is at an H level.
A timing pulse generating circuit that outputs sampling and second sampling when the lighting pulse signal is at the L level, and is connected to the timing pulse generating circuit and blinks by the lighting pulse signal from the timing pulse generating circuit, and A light source in which the incident light on the glass surface is made nearly parallel to the glass surface to increase the incident angle, and the light receiving axis is removed from the reflection position of the light emitted from the light source from the glass surface to the glass surface in front of the camera lens. A light sensor for receiving diffusely reflected light from the windshield of the light from the light source, and a filter having a frequency band corresponding to the frequency of the lighting pulse signal and connected to the signal output terminal of the light sensor. And a timing pulse generating circuit connected to the band pass filter and the timing pulse generating circuit. First sampling and holding circuit for holding the output signal value of the bandpass filter by the first sampling pulse of the bandpass filter, and the bandpass filter by the second sampling pulse from the timing pulse generating circuit connected to the bandpass filter and the timing pulse generating circuit. Connected to the first sampling and holding circuit and the second sampling and holding circuit to hold the output signal value of the second sampling and holding circuit and the difference between the holding value of the first sampling and holding circuit and the holding value of the second sampling and holding circuit. A dew condensation detecting device for a camera case, comprising a voltage comparing means for outputting an ON signal when a reference value is exceeded. 2. A vertical sync separation circuit connected to a video camera, wherein the timing pulse generation circuit is connected to the vertical sync separation circuit, and the synchronization signal output from the vertical sync separation circuit is input to the timing pulse generation circuit. The cycle of the lighting pulse signal and the first sampling pulse and the second sampling pulse output from the timing generation circuit using the synchronization signal as a trigger is adjusted to the vertical synchronization signal. Condensation detection device. 3. A lighting pulse signal is output at a constant frequency, and when the lighting pulse signal is at H level, the first
A timing pulse generating circuit that outputs sampling and second sampling when the lighting pulse signal is at the L level, and is connected to the timing pulse generating circuit and blinks by the lighting pulse signal from the timing pulse generating circuit, and It is connected to a video signal output signal terminal of a video camera, which is a light source in which the incident light on the glass surface is made nearly parallel to the glass surface to increase the incident angle and a filter of a frequency band corresponding to the frequency of the lighting pulse signal. A bandpass filter, a first sampling hold circuit connected to the bandpass filter and the timing pulse generating circuit, for holding an output signal value of the bandpass filter by a first sampling pulse from the timing pulse generating circuit, and the bandpass filter Connected to filter and timing pulse generator A second sampling hold circuit that holds the output signal value of the bandpass filter by the second sampling pulse from the timing pulse generation circuit, and a hold of the first sampling hold circuit connected to the first sampling hold circuit and the second sampling hold circuit A dew condensation detecting device for a camera case, comprising voltage comparison means for outputting an ON signal when a difference between the value and the hold value of the second sampling and holding circuit exceeds a reference value.