JP4345048B2 - Lighting apparatus and method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an illuminating device and method used when photographing a monitoring place with an imaging device, and more particularly to an illuminating device and method in which an illuminating unit that illuminates the monitoring place and a photometric unit that measures illuminance are provided in the apparatus. .
[0002]
[Prior art]
In recent years, surveillance imaging devices (cameras) are often installed for crime prevention in financial institutions such as banks, stores such as supermarkets and convenience stores, amusement facilities such as pachinko stores, and parking lots. Some cameras of this type are referred to as day / night continuous cameras that have a visible light photographing mode and an infrared light photographing mode, and are capable of photographing day and night. In some cases, the camera alone cannot perform sufficient monitoring, and in order to perform sufficient monitoring, an illumination device for illuminating the range captured by the camera may be used. An LED is often used as an illumination element used in the illumination device (for example, Patent Document 1).
[0003]
In addition, since constantly illuminating a monitoring place is a waste of electric power, there is one that detects the brightness of the monitoring place and turns on the lighting device when it is dark when illumination is necessary (for example, Patent Document 2). .
[0004]
By the way, the illuminating device can illuminate the subject brighter if it is arranged near the subject (monitoring place). However, it is necessary to arrange the camera at a position away from the monitoring place so that the monitoring place can be seen. Therefore, it is preferable to separate the camera and the lighting device and eliminate mutual connection. At this time, it is necessary to provide an illumination unit that illuminates the monitoring place and a photometric unit that measures illuminance in the same illumination device.
[0005]
4A and 4B are perspective views showing an example of a conventional lighting device, in which FIG. 4A is a view of the lighting device viewed from the front side, and FIG. 4B is a view of the lighting device viewed from the back side. As shown in FIG. 4A, a plurality of LEDs 2 are arranged on the front surface of the lighting device 1. Although the state where the cover 4 is removed is shown here, the cover 4 is attached to the front surface of the lighting device 1 so as to cover the LED 2.
[0006]
As shown in FIG. 4B, a photometric unit 3 made of a photodiode is disposed on the back surface of the illumination device 1. The reason why the photometry unit 3 is provided on the back surface of the illumination device 1 is as follows. Sufficient light shielding is required between the illuminating unit by the LED 2 and the photometric unit 3, and the illuminating unit by the LED 2 and the photometric unit 3 are separated so that the photometric unit 3 is not affected by the illumination by the LED 2.
[0007]
[Patent Document 1]
JP-A-5-328210 [Patent Document 2]
JP-A-7-37175 [0008]
[Problems to be solved by the invention]
In this type of conventional illumination device, if the light metering unit is not sufficiently shielded from the illumination unit, the following problems occur. That is, when the photometry unit determines that the monitoring place is dark, the illumination unit turns on the illumination. Then, simultaneously with the lighting, the illumination is measured by the photometry unit, the photometry unit determines that the monitoring place is bright, and the illumination unit turns off the illumination. Furthermore, since the illumination disappears at the same time as the light is turned off, the photometry unit determines that the monitoring place is dark again, and the illumination unit turns on the illumination. In this way, a phenomenon called a hunting phenomenon or chattering phenomenon occurs in which the illumination unit alternately turns on and off.
[0009]
As described above, in an illuminating device having an illuminating unit and a photometric unit, a hunting phenomenon (chattering phenomenon) may occur. Therefore, it is necessary to sufficiently block light from the illuminating unit to the photometric unit. Therefore, it is difficult to arrange the illumination unit and the photometry unit in the same direction, and the configuration as shown in FIG. For this reason, if the illumination unit is directed to the subject, the photometry unit cannot be directed to the subject, and the illuminance in the vicinity of the subject cannot be measured, so that the lighting on / off cannot be controlled with high accuracy. There was a point. Further, since the photometry unit and the illumination unit cannot be provided on the same substrate, there is a problem that the cost is increased.
[0010]
The present invention has been made in view of such problems, and an illuminating device in which an illuminating unit and a photometric unit can be arranged in the same direction, and lighting on / off can be controlled with high accuracy, and It aims to provide a method. It is another object of the present invention to provide an illuminating device and method that can be provided on the same substrate without restrictions on the arrangement of the illuminating unit and the photometric unit, and can be reduced in cost.
[0011]
[Means for Solving the Problems]
The present invention solves the above-mentioned problems of the prior art,
(A) In an illuminating device that illuminates a photographing location photographed by an imaging device, an illuminating means (12) that illuminates the photographing location and the illumination means are arranged in substantially the same direction, and the illuminance at the photographing location is measured The photometric means (13) for driving, the driving means (24) for driving the lighting means to be in a lighting state in which the lighting means blinks at a frequency higher than the field frequency of the video signal photographed by the imaging device, and the lighting means flashes. Using the measurement result of the photometry means during the period corresponding to the extinction period when the light is turned on, it is determined whether the illumination means should be turned on or the illumination means should be turned off. Based on the determination result by the determination means (23) and the determination means, the lighting means is turned on by the driving means, or the illumination by the driving means. Providing a lighting device which is characterized by being configured and control means for switching whether the means unlit (23, 24),
(B) In an illumination method used for an illuminating device that illuminates a photographing location photographed by an imaging device, the photographing is performed by photometry means (13) arranged in substantially the same direction as an illuminating means (12) that illuminates the photographing location. A measurement step of measuring the illuminance of the place, and a measurement by the photometry step within a period corresponding to the extinction period when the illumination means is blinked at a frequency higher than the field frequency of the video signal photographed by the imaging device Using the result, a determination step for determining whether the lighting unit should be in a lighting state that blinks at the frequency, or whether the lighting unit should be in a light-off state that is always off, and the determination result by the determination step And a control step for switching whether to turn on the lighting means or turn off the lighting means. There is provided an illumination method comprising.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the lighting apparatus and method of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram showing an embodiment of the illumination device of the present invention, FIG. 2 is an exploded perspective view showing an embodiment of the illumination device of the present invention, and FIG. 3 is a diagram for explaining the illumination device and method of the present invention. It is a waveform diagram.
[0013]
First, the external configuration of an embodiment of the illumination device of the present invention will be described with reference to FIG. As shown in FIG. 2, a plurality (27 in the present embodiment) of LEDs 12 that are light emitting elements are arranged on the front surface of the lighting device 11. Here, a state in which the cover 14 is removed is illustrated, but the cover 14 is attached to the front surface of the lighting device 11 so as to cover the LEDs 12. On the same surface as the surface on which the LED 12 is disposed, and on the front surface of the illuminating device 11, for example, a photometric unit 13 made of a photodiode (light receiving element) is disposed.
[0014]
The cover 14 attached to the front surface of the lighting device 11 is formed so as to block visible light and transmit infrared light. Even if the LED 12 emits not only infrared light but also visible light, the visible light is blocked by the cover 14 and only the infrared light is projected to the outside. Therefore, even if the lighting device 11 is turned on, it does not stand out from the outside. Furthermore, when the cover 14 is mounted on the front surface of the lighting device 11, the portion facing the photometric unit 13 is a transparent unit 15 that transmits visible light and infrared light. The photometry unit 13 measures all the light received by the imaging device and switches on / off of the LED 12 that is the illumination unit, and therefore receives both visible light and infrared light through the transparent unit 15.
[0015]
The LED 12 and the photometry unit 13 are provided on the same substrate (not shown), and no light shielding object is provided between them. As shown in FIG. 2, the LED 12 and the photometry unit 13 face the same direction. The illumination device 11 is installed so that the LED 12 and the photometry unit 13 face the subject.
[0016]
Next, the circuit configuration of an embodiment of the illumination device of the present invention will be described with reference to FIG. In FIG. 1, the same parts as those in FIG. In FIG. 1, the LED 12 is partially illustrated for simplification. The illumination method of the present invention which is the operation of FIG. 1 will also be described using the waveform diagram of FIG. In FIG. 1, a photodiode output amplifying unit 21 is connected to a photometric unit 13 made of a photodiode. The light reception output by the photometry unit 13 is amplified by the photodiode output amplification unit 21 and output as photometry data.
[0017]
The reference pulse generator 22 generates a reference pulse shown in FIG. As shown in FIG. 3A, the reference pulse is, for example, a pulse having a cycle of 3.33 mS (frequency: 300 Hz) with an on period of 2.22 mS and an off period of 1.11 mS. And supplied to the LED driving unit 24. Note that the reference pulse generation unit 22 and the brightness determination unit 23 can be configured by a microprocessor incorporating an A / D converter.
[0018]
If the LED driving unit 24 is operated by the reference pulse shown in FIG. 3A and the LED 12 blinks at 300 Hz, the photometric unit 13 receives external light including light emitted from the LED 12 (light emission). . At this time, the photometric data that is the output of the photodiode output amplifier 21 is as shown in FIG. As shown in FIG. 3B, the output of the photodiode output amplifying unit 21 is generally pulsed as shown in FIG. 3A, but the portion T1 affected by the lighting of the LED 12, the afterglow of the LED 12, and the circuit The portion T2 is affected by the responsiveness of the LED 12, and the portion T3 is not affected by the lighting of the LED 12 when the LED 12 is turned off.
[0019]
The photometric data shown in FIG. 3B output from the photodiode output amplification unit 21 is supplied to the brightness determination unit 23. The brightness determination unit 23 generates a photometric timing pulse shown in FIG. 3C using the reference pulse shown in FIG. The period in which the photometric timing pulse is high corresponds to the period T3 of the photometric data shown in FIG. 3B (the extinction period during which the LED 12 is blinking). The brightness determination unit 23 sets the period when the photometry timing pulse is high as the brightness determination period, and the photometry data from the photodiode output amplification unit 21 exceeds the predetermined threshold shown in FIG. Determine whether or not.
[0020]
The brightness determination unit 23 compares the photometric data with the threshold value, and if it is determined that the photometric data exceeds the threshold value, the LED 12 is turned off, and the photometric data is determined to be less than or equal to the threshold value. If the LED 12 is turned on, a light on / off control signal is generated and supplied to the LED drive unit 24. The LED drive unit 24 turns on the LED 12 based on the reference pulse from the reference pulse generation unit 22 when the turn-on / off control signal from the brightness determination unit 23 is a control signal to turn on the LED 12. As described above, the LED 12 actually flashes at 300 Hz.
[0021]
On the other hand, the LED drive unit 24 turns off the LED 12 when the turn-on / off control signal from the brightness determination unit 23 is a control signal for turning off the LED 12.
[0022]
By the way, the reason why the blinking frequency of the LED 12 is set to 300 Hz is as follows. An imaging device (not shown) used together with the illumination device 11 captures a video signal at a field frequency of 60 Hz in the NTSC system. In the PAL system, a video signal is shot at a field frequency of 50 Hz. If the blinking frequency of the LED 12 is 300 Hz, illumination and photometry can be performed five times in one field period in the case of the NTSC system. In the case of the PAL method, illumination and photometry can be performed six times in one field period.
[0023]
The fluorescent lamp blinks at the frequency of the power supply (50 Hz or 60 Hz in Japan), but if it is a high frequency of about 300 Hz, it is not affected by the flicker of the fluorescent lamp. Since at least 5 photometry can be performed per field, the LED 12 may be switched on and off by using an average of the values measured at the 5 times. In this way, it is not affected by the flicker of the fluorescent lamp.
[0024]
Thus, the blinking frequency of the LED 12 is preferably an integer multiple of the field frequency of 60 Hz in the case of an NTSC imaging device. In the case of a PAL imaging device, it is preferably an integer multiple of a field frequency of 50 Hz. More preferably, it is a common multiple of 60 Hz and 50 Hz. The blinking frequency of the LED 12 is not limited to 300 Hz which is the least common multiple of 60 Hz and 50 Hz, and may be an integer multiple of 300 Hz.
[0025]
【The invention's effect】
As described above in detail, the illumination apparatus and method of the present invention measures the illuminance at the photographing location by the photometric means arranged in substantially the same direction as the illumination means for illuminating the photographing location, and the illumination means is used as the imaging device. The lighting means blinks at a high frequency using the measurement result of the photometric means (step) within the period corresponding to the extinction period when blinking at a frequency higher than the field frequency of the video signal to be photographed by It is determined whether or not the lighting unit should be turned off or the lighting unit should be turned off at all times, and based on the determination result, the lighting unit is turned on or the lighting unit is turned off. As a result, the illumination means and the photometry means can be arranged in the same direction, and the illumination point can be accurately detected without causing a hunting phenomenon (chattering phenomenon). - it is possible to control the off.
[0026]
Further, no light shielding structure is required between the illumination unit and the photometry unit, and there is no restriction on the arrangement of the illumination unit and the photometry unit, and they can be provided on the same substrate. Therefore, the cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of a lighting device of the present invention.
FIG. 2 is an exploded perspective view showing an embodiment of a lighting device according to the present invention.
FIG. 3 is a waveform diagram for explaining an illumination apparatus and method according to the present invention.
FIG. 4 is an exploded perspective view showing a conventional example.
[Explanation of symbols]
11 Illumination device 12 LED (illumination unit, illumination means)
13 Metering unit (Measuring means)
14 Cover 15 Transparent part 21 Photodiode output amplification part 22 Reference pulse generation part 23 Brightness determination part (determination means, control means)
24 LED drive unit (drive means, control means)

Claims (4)

In a lighting device that illuminates a shooting location for shooting by an imaging device,
Illumination means for illuminating the shooting location;
A photometric means that is arranged in substantially the same direction as the illuminating means, and measures the illuminance at the photographing location;
Driving means for driving the illumination means to be in a lighting state in which the lighting means blinks at a frequency higher than a field frequency of a video signal photographed by the imaging device;
Using the measurement result by the photometry means in a period corresponding to the extinction period when the illumination means blinks, the illumination means should be turned on, or the illumination means is always turned off and A determination means for determining whether to do;
And a control unit that switches whether the lighting unit is turned on by the driving unit or the lighting unit is turned off by the driving unit based on a determination result by the determining unit. A lighting device. The lighting device according to claim 1, wherein a frequency of blinking in the lighting state of the lighting unit is approximately 300 Hz or an integral multiple thereof. In an illumination method for use in an illumination device that illuminates a photographing location for photographing by an imaging device,
A measurement step of measuring the illuminance at the shooting location by photometry means arranged in substantially the same direction as the illumination means for illuminating the shooting location;
When the illumination means is blinked at a frequency higher than the field frequency of the video signal photographed by the imaging device, the illumination means is used by using the measurement result of the photometry step in the period corresponding to the extinction period. A determination step for determining whether the lighting state should be blinked at a frequency, or whether the lighting means should be in an extinguished state that is constantly extinguished,
And a control step of switching whether to turn on the lighting unit or turn off the lighting unit based on the determination result of the determining step. The lighting method according to claim 3, wherein a frequency of blinking in the lighting state of the lighting unit is approximately 300 Hz or an integer multiple thereof.

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