JP2004191489A - Illuminator and illuminating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an illuminator where an illumination part and a photometry part are arranged to be faced in the same direction and which accurately controls the turn-on/turn-off of illumination. <P>SOLUTION: An LED 12 illuminates a photographic place photographed by an imaging apparatus. The photometry part 13 is arranged to face nearly in the same direction as the LED 12 and measures the illuminance of the photographic place. An LED driving part 24 sets a lit state where the LED 12 is flickered at frequency higher than the field frequency of a video signal obtained by photographing by the imaging apparatus. A brightness decision part 23 decides whether to set the LED 12 to the lit state or an unlit state by using the result of measurement by the photometry part 13 in a period equivalent to the unlit period of the LED 12's flickering time. The driving part 24 switches the lit state/the unlit state based on the result of decision by the decision part 23. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an illuminating device and a method used when capturing an image of a monitoring place by an imaging device, and more particularly to an illuminating device and a method in which an illuminating unit for illuminating a monitoring place and a photometric unit for measuring illuminance are provided in the apparatus. .
[0002]
[Prior art]
2. Description of the Related Art In recent years, surveillance imaging devices (cameras) have often been installed for financial security, such as financial institutions such as banks, stores such as supermarkets and convenience stores, play facilities such as pachinko parlors, and parking lots. Some cameras of this type include a visible light photographing mode and an infrared light photographing mode, and are referred to as day and night continuous cameras capable of photographing during the day and at night. In some cases, the camera alone cannot perform sufficient monitoring, and in order to perform sufficient monitoring, an illuminating device for illuminating an area captured by the camera may be used. An LED is often used as a lighting element used in a lighting device (for example, Patent Document 1).
[0003]
In addition, since it is a waste of power to constantly illuminate the monitoring place, there is an apparatus that detects the brightness of the monitoring place and turns on the lighting device when the lighting is dark (for example, Patent Document 2). .
[0004]
By the way, the illuminating device can be illuminated more brightly when it is arranged near the subject (monitoring place). However, the camera needs to be arranged at a position remote from the surveillance place so that the camera can overlook the surveillance place. Therefore, it is preferable that the camera and the lighting device are separated from each other so that they are not connected to each other. At this time, it is necessary to provide a lighting unit for illuminating the monitoring place and a photometric unit for measuring illuminance in the same lighting device.
[0005]
4A and 4B are perspective views illustrating an example of a conventional lighting device. FIG. 4A is a diagram of the lighting device as viewed from the front side, and FIG. 4B is a diagram of the lighting device as 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. Here, the state where the cover 4 is removed is illustrated, but 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 composed of a photodiode is arranged on the back surface of the lighting device 1. The reason why the photometric unit 3 is provided on the back surface of the lighting 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
[Problems to be solved by the invention]
In this type of conventional illuminating device, if the light from the illuminating unit is not sufficiently shielded from the light metering unit, the following problem occurs. That is, when the photometry unit determines that the monitoring place is dark, the illumination unit turns on the illumination. Then, at the same time as 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. Further, since the illumination is turned off at the same time as the light is turned off, the photometry unit again determines that the monitoring place is dark, and the illumination unit turns on the illumination. As described above, a phenomenon called a hunting phenomenon or a chattering phenomenon occurs in which the lighting unit alternately turns on and off.
[0009]
As described above, in a lighting device having an illumination unit and a photometric unit, there is a possibility that a hunting phenomenon (a chattering phenomenon) may occur. Therefore, it is necessary to sufficiently shield the photometric unit from light from the illumination unit. Therefore, it is difficult to arrange the illuminating unit and the photometric unit in the same direction, and it has to be configured as shown in FIG. For this reason, when the illumination unit is aimed at the subject, the photometry unit cannot be aimed at the subject, and the illuminance near the subject cannot be measured, so that the lighting on / off cannot be controlled with high accuracy. There was a point. In addition, since the photometric unit and the illuminating unit cannot be provided on the same substrate, there is a problem that the cost is high.
[0010]
The present invention has been made in view of such a problem, an illumination device that can arrange an illumination unit and a photometry unit in the same direction, and can control lighting on and off with high accuracy. The aim is 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 any restriction on the arrangement of the illuminating unit and the photometric unit, and can be manufactured at low cost.
[0011]
[Means for Solving the Problems]
The present invention has been made to solve the above-mentioned problems of the related art.
(A) In a lighting device for illuminating a shooting location where an image is taken by an imaging device, an illuminating means (12) for illuminating the shooting location is disposed substantially in the same direction as the illuminating means, and the illuminance of the shooting location is measured. A light metering means (13), a 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 a field frequency of a video signal photographed by the imaging device; It is determined whether the lighting means should be turned on or the lighting means should be kept turned off by using the measurement result by the photometric means within a period corresponding to the period of extinction when the lighting is performed. And determining whether the lighting means is in the lighting state by the driving means or the lighting means by the driving means based on the determination result by the determining 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 illumination device for illuminating an imaging location where an image is captured by an imaging device, the photometric device (13) arranged in substantially the same direction as the illumination device (12) for illuminating the imaging location may be used. A measurement step of measuring the illuminance of a place, and the measurement by the photometry step during a period corresponding to a period of extinction when the lighting unit is blinked at a frequency higher than a field frequency of a video signal captured by the imaging device. Using the result, a determination step of determining whether the lighting means should be in a lighting state in which the lighting means blinks at the frequency, or a lighting state in which the lighting means should be constantly turned off, and a determination result by the determination step Controlling whether the lighting means is turned on or off based on the lighting means. There is provided an illumination method comprising.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a lighting device and a 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 lighting device of the present invention, FIG. 2 is an exploded perspective view showing an embodiment of the lighting device of the present invention, and FIG. 3 is a diagram for explaining the lighting device and method of the present invention. It is a waveform diagram.
[0013]
First, the external configuration of an embodiment of the lighting device of the present invention will be described with reference to FIG. As shown in FIG. 2, a plurality of (in this embodiment, 27) LEDs 12 that are light emitting elements are arranged on the front surface of the lighting device 11. Here, the state where 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 LED 12. On the same surface as the surface on which the LEDs 12 are arranged, and on the front surface of the illuminating device 11, a photometric unit 13 composed of, for example, a photodiode (light receiving element) is arranged.
[0014]
The cover 14 mounted on 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 is not noticeable from the outside. Further, when the cover 14 is mounted on the front surface of the lighting device 11, a portion facing the photometric unit 13 is a transparent unit 15 that transmits visible light and infrared light. The photometric unit 13 needs to measure all the light received by the imaging device and switch on and off the LED 12 serving as the illumination unit. Therefore, the photometric unit 13 receives both visible light and infrared light through the transparent unit 15.
[0015]
The LED 12 and the photometric unit 13 are provided on the same substrate (not shown), and no light-shielding member or the like is provided between the two. As shown in FIG. 2, the LED 12 and the photometric unit 13 face in the same direction. The lighting 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 lighting device of the present invention will be described with reference to FIG. 1, the same parts as those in FIG. 2 are denoted by the same reference numerals. 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 be described with reference to the waveform diagram of FIG. In FIG. 1, a photodiode output amplifying section 21 is connected to a photometric section 13 composed of a photodiode. The received light output by the photometric unit 13 is amplified by the photodiode output amplifying unit 21 and output as photometric 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 with a period of 3.32 mS (frequency 300 Hz) having an on period of 2.22 mS and an off period of 1.11 mS. Is supplied to the LED drive unit 24. The reference pulse generator 22 and the brightness determiner 23 can be configured by a microprocessor having an A / D converter.
[0018]
Assuming that the LED driving unit 24 is operated by the reference pulse shown in FIG. 3A and the LED 12 blinks at 300 Hz, the photometry unit 13 receives external light including light by lighting (light emission) of the LED 12. . At this time, the photometric data which 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 section 21 has a pulse shape 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 And a portion T3 which is not affected by the lighting of the LED 12 due to the turning off of the LED 12.
[0019]
The photometric data shown in FIG. 3B output from the photodiode output amplifying unit 21 is supplied to the brightness determining unit 23. The brightness determination unit 23 generates a photometric timing pulse illustrated in FIG. 3C using the reference pulse illustrated in FIG. The period during which the photometric timing pulse is high corresponds to the period of the portion T3 of the photometric data shown in FIG. Then, the brightness determination unit 23 sets the period in which the photometric timing pulse is high as the brightness determination period, and the photometric data from the photodiode output amplifying unit 21 exceeds the predetermined threshold value shown in FIG. Is determined.
[0020]
By comparing the photometric data with the threshold value, the brightness determination unit 23 turns off the LED 12 if it is determined that the photometric data exceeds the threshold value, and determines that the photometric data is equal to or less than the threshold value. For example, an ON / OFF control signal is generated and supplied to the LED drive unit 24 so that the LED 12 is turned on. 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 for turning on the LED 12. As described above, the LED 12 actually blinks at 300 Hz.
[0021]
On the other hand, the LED drive unit 24 turns off the LED 12 when the turn-on / turn-off control signal from the brightness determination unit 23 is a control signal for turning off the LED 12.
[0022]
The blinking frequency of the LED 12 is set to 300 Hz for the following reason. 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 method, a video signal is photographed at a field frequency of 50 Hz. If the blinking frequency of the LED 12 is 300 Hz, in the case of the NTSC system, illumination and photometry can be performed five times in one field period. In the case of the PAL system, 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 is not affected by the flicker of the fluorescent lamp at a high frequency of about 300 Hz. Since at least five photometry operations can be performed per field, the on / off state of the LED 12 may be switched by using an average of the five photometric values. In this way, there is no influence of the flicker of the fluorescent lamp.
[0024]
As described above, the blinking frequency of the LED 12 is preferably an integral multiple of the field frequency of 60 Hz in the case of an imaging device of the NTSC system. In the case of a PAL type imaging device, it is preferable that the field frequency be an integral multiple 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 in detail above, the lighting device and method of the present invention measure the illuminance of the shooting place by the photometric means arranged in substantially the same direction as the lighting means for illuminating the shooting place, and set the lighting means to the imaging device. Lighting which blinks the illumination means at the higher frequency using the measurement result by the photometric means (step) during the period corresponding to the extinction period when the flickering is performed at a higher frequency than the field frequency of the video signal to be photographed. It is determined whether the state should be in the state or the state in which the lighting means should be always turned off. Based on the result of the determination, it is switched between the state in which the lighting means is turned on and the state in which the lighting means is turned off. As a result, the illuminating means and the photometric means can be arranged in the same direction, and the illuminating point and the light measuring point can be accurately determined without causing a hunting phenomenon (chattering phenomenon). - it is possible to control the off.
[0026]
In addition, a light-blocking structure is not required between the lighting means and the photometric means, and there is no restriction on the arrangement of the lighting means and the photometric means, 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 one embodiment of a lighting device of the present invention.
FIG. 2 is an exploded perspective view showing an embodiment of the lighting device of the present invention.
FIG. 3 is a waveform diagram for explaining the lighting device and method of the present invention.
FIG. 4 is an exploded perspective view showing a conventional example.
[Explanation of symbols]
11 lighting device 12 LED (lighting unit, lighting means)
13 Photometry unit (photometry 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 place where shooting is performed by an imaging device,
Lighting means for illuminating the shooting location;
Light metering means arranged in substantially the same direction as the lighting means, and measuring the illuminance of the shooting location,
A driving unit that drives the lighting unit to be in a lighting state in which the lighting unit blinks at a frequency higher than a field frequency of a video signal captured by the imaging device,
Using the measurement result by the photometric unit in a period corresponding to a period of extinguishing when the lighting unit blinks, whether the lighting unit should be turned on, or an unlit state in which the lighting unit is always turned off. Determining means for determining whether to perform,
Control means for switching whether the lighting means is turned on by the driving means or the lighting means is turned off by the driving means based on a result of the judgment by the judging means. Lighting equipment. 2. The lighting device according to claim 1, wherein the blinking frequency of the lighting unit in the lighting state is approximately 300 Hz or an integer multiple thereof. In a lighting method used for a lighting device that illuminates a shooting location to be shot by an imaging device,
A measuring step of measuring the illuminance of the shooting location by photometric means arranged in substantially the same direction as the illumination means for illuminating the shooting location,
When the illuminating unit is turned on and off at a frequency higher than the field frequency of the video signal captured by the imaging device, the illuminating unit is illuminated by using the measurement result obtained by the photometry step within a period corresponding to a extinction period. A determination step to determine whether to be in a lighting state to blink at a frequency or to be in an unlit state in which the lighting means is always turned off,
A control step of switching between turning on the lighting unit and turning off the lighting unit based on a result of the determination in the determining step. 4. The lighting method according to claim 3, wherein the blinking frequency of the lighting unit in the lighting state is approximately 300 Hz or an integer multiple thereof.

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