JP2018022980A - Monitor camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a monitor camera ensuring good imaging, even when the temperature in the monitor camera or the temperature around the monitor camera changed.SOLUTION: A monitoring camera (1) includes an LED lighting (5) irradiating outgoing light (L1), a filter placed oppositely to the LED lighting (5), and converting only the outgoing light (L1) of specific wavelength into transmitted light (L2), and an imaging sensor (2) performing photoelectric conversion of reflection light (L3) of the transmitted light (L2) reflected on a subject (6). The LED lighting (5) includes multiple LEDs (51-53) so as to have the light of continuous peak wavelength in a wavelength region wider than the sensitivity wavelength region of the imaging sensor (2). Peak wavelength in the spectral characteristics of the transmitted light (L2) is the same as the peak sensitivity wavelength in the spectral sensitivity characteristics of the imaging sensor (2).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a surveillance camera having a light source.

  The surveillance camera has a light source, thereby enabling clearer and better imaging. In particular, photographing at night is often performed by irradiating an infrared LED or the like because the amount of light irradiating the subject is insufficient. However, since the wavelength of light that illuminates the subject differs between shooting under sunlight in the daytime and shooting using an infrared LED or the like at night, the daytime and nighttime can be used to shoot a good image. It is necessary to change the surveillance camera settings.

  On the other hand, in the technique disclosed in Patent Document 1, as an operation of the surveillance camera, shooting is performed using an infrared cut filter during the daytime, and shooting is performed without using the infrared cut filter at night. Specifically, an infrared cut filter that cuts infrared light, an insertion / removal unit that inserts / removes the infrared cut filter into / from the optical path of the imaging optical system, and the brightness of the subject are provided at different locations from the imaging unit. A brightness detecting means for detecting the light intensity and a control means for controlling the insertion / removal of the insertion / removal means. The control means inserts the brightness information of the brightness detection means and the infrared cut filter into the optical path of the imaging optical system. The insertion / removal means is controlled based on a difference in lightness information of a region corresponding to the lightness detection range of the image pickup means obtained in a state where the image pickup means is not present and a predetermined switching determination threshold.

  As a result, in the technique disclosed in Patent Document 1, the imaging range of the imaging optical system changes greatly even if a brightness detection unit that is provided in a different part from the imaging optical system and whose detection range is fixed is used. Even so, at least two imaging modes can be switched stably by inserting and removing the infrared cut filter.

  In the technique disclosed in Patent Document 2, the wavelength band of the infrared light to be irradiated is selected by selecting one of a plurality of infrared bandpass filters for irradiation each having a passband that does not overlap with each other. The wavelength band of the reflected light to be photographed is selected by selecting one of a plurality of photographing infrared bandpass filters each having a pass band that does not overlap each other. Also, the infrared bandpass filter for irradiation and the infrared bandpass filter for photographing are selected to have the same wavelength band, and the wavelength band different from the oncoming vehicle is selected.

  Thereby, in the technique disclosed in Patent Document 2, it is possible to prevent the halation of the camera due to the irradiation of infrared light from the oncoming vehicle without precise control.

  Furthermore, in the technique disclosed in Patent Document 3, the object is illuminated by the illuminating unit, an image of a predetermined shape is projected onto the object by the projecting unit, and the position of the object is observed while visually observing the projected image. By adjusting the relationship, it is possible to set a predetermined area on the object and adjust the focus. Of the light reflected from the object, light in a wavelength band other than the wavelength band of the projected image is selected (incident or reflected) by the wavelength selection element, and an image formed by the selected light is captured by the imaging means.

  Thereby, in the technique disclosed in Patent Literature 3, it is possible to perform setting and focusing of a predetermined area of the object without using a display device, and to perform imaging and inspection of the object.

Japanese Patent No. 5014474 (issued August 29, 2012) Japanese Patent No. 4033008 (issued on January 16, 2008) Japanese Patent No. 3516006 (issued on April 5, 2004)

  However, in the techniques of Patent Documents 1 to 3, the wavelength shift of the light source occurs due to the temperature change in the camera and the temperature change around the camera, and the peak sensitivity wavelength of the spectral sensitivity characteristic of the image sensor and the light emitted from the light source There is a problem that the peak wavelength of the spectral characteristics does not coincide with each other, and good imaging cannot be obtained.

  The present invention has been made in view of the above-described problems, and its purpose is to obtain good imaging even when the temperature in the surveillance camera or the temperature around the surveillance camera changes. Is to realize a simple surveillance camera.

  In order to solve the above-described problem, a monitoring camera according to one aspect of the present invention is arranged so as to face an LED illumination that emits emitted light and the LED illumination, and only the emitted light having a specific wavelength is transmitted light. A filter for converting, and an imaging sensor that photoelectrically converts the reflected light of the transmitted light reflected by the subject, and the LED illumination has a continuous peak wavelength in a wavelength region wider than a sensitivity wavelength region of the imaging sensor. A plurality of LEDs are provided so as to have light, and the peak wavelength in the spectral characteristic of the transmitted light is the same as the peak sensitivity wavelength in the spectral sensitivity characteristic of the imaging sensor.

  In order to solve the above problems, a monitoring camera according to another aspect of the present invention includes an LED illumination that irradiates outgoing light, reflected light that is reflected from a subject, and the reflected light that is incident on the subject. An imaging sensor that performs photoelectric conversion, and a control unit that selects and operates a plurality of LEDs provided in the LED illumination so as to have continuous peak wavelength light in a wavelength region wider than a sensitivity wavelength region of the imaging sensor. The LED illumination includes a plurality of temperature sensors that measure the temperature of each of the plurality of LEDs, and the control unit is configured based on the temperatures measured by the plurality of temperature sensors. Only the first LED, which is an LED having light having a wavelength closest to the peak sensitivity wavelength in the spectral sensitivity characteristic of the imaging sensor, is selected and operated.

  According to one aspect of the present invention, there is an effect of realizing a surveillance camera capable of obtaining good imaging even when the temperature in the surveillance camera or the temperature around the surveillance camera changes.

It is a block diagram which shows the structure of the surveillance camera which concerns on Embodiment 1 of this invention. It is a characteristic view which shows the relationship between temperature and the wavelength of one LED of a LED group. (A) is a characteristic diagram which shows the spectral sensitivity characteristic of the imaging | photography sensor before the temperature change in a surveillance camera, (b) is a spectral characteristic of the light irradiated from one LED group before the temperature change in a surveillance camera. FIG. (A) is a characteristic diagram which shows the spectral sensitivity characteristic of the imaging | photography sensor after the temperature change in a surveillance camera, (b) is the spectral characteristic of the light irradiated from one LED group after the temperature change in a surveillance camera. FIG. (A) is a characteristic diagram showing the spectral sensitivity characteristics of the imaging sensor, (b) is a characteristic chart showing the spectral transmission characteristics of the light transmission filter, and (c) is a spectrum of light emitted from the three LED groups. It is a characteristic view which shows a characteristic. It is a characteristic view which shows the relationship between temperature and the wavelength of three LED selected one each from three LED groups. (A) is a block diagram which shows the structure of the surveillance camera which concerns on Embodiment 2 of this invention, (b) is an enlarged view of LED illumination shown to (a). (A) is a characteristic diagram which shows the spectral sensitivity characteristic of an imaging sensor, (b)-(d) is a characteristic diagram which shows the spectral characteristic of the light irradiated from LED group, respectively.

Embodiment 1
An embodiment of the present invention will be described below with reference to FIGS. Many surveillance cameras shoot subjects using LED illumination. The surveillance camera of the present invention photographs an object using LED illumination as a light source.

(Schematic configuration of surveillance camera 1)
First, a schematic configuration of the surveillance camera 1 according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing the structure of a surveillance camera 1 according to Embodiment 1 of the present invention.

  As shown in FIG. 1, the surveillance camera 1 includes an imaging sensor 2, a light transmission filter 3 (filter), a power supply 4, and an LED illumination 5.

  The imaging sensor 2 includes an on-chip color filter 21, and the reflected light L3, which is the transmitted light L2 reflected by the subject 6, enters, and photoelectrically converts the reflected light L3. The imaging sensor 2 captures the state of the subject 6 captured by the monitoring camera 1 as an image by photoelectrically converting the reflected light L3 obtained by reflecting the transmitted light L2 on the subject 6. The image sensor 2 is connected to a power source 4, and power necessary for the operation of the image sensor 2 is supplied from the power source 4.

  The on-chip color filter 21 is provided in the image sensor 2 on the side where the image sensor 2 receives the reflected light L3. The on-chip color filter 21 transmits the transmitted light L2 reflected by the subject 6, and the imaging sensor 2 photoelectrically converts the transmitted reflected light L3. The on-chip color filter 21 transmits only the light having a specific wavelength corresponding to the spectral transmission characteristic of the on-chip color filter 21 by transmitting the reflected light L3 reflected by the subject 6 through the transmitted light L2. Since the transmittance peak wavelength in the spectral transmission characteristic of the on-chip color filter 21 is the same as the peak sensitivity wavelength in the spectral sensitivity characteristic of the imaging sensor 2, in the spectral characteristic of the reflected light L3 transmitted through the on-chip color filter 21. The peak wavelength is the same as the peak sensitivity wavelength in the spectral sensitivity characteristic of the image sensor 2. Thereby, since the imaging sensor 2 receives the reflected light L3 having light having the same wavelength as the peak sensitivity wavelength in the spectral sensitivity characteristic of the imaging sensor 2, the monitoring camera 1 can obtain good imaging.

  The light transmission filter 3 transmits only the specific wavelength of the emitted light L1 emitted from the LED illumination 5, and converts the emitted light L1 into the transmitted light L2. The light transmission filter 3 is disposed so as to face the LED illumination 5. Specifically, the light transmission filter 3 is provided so as to cover the direction in which the LED illumination 5 irradiates the emitted light L1. Further, the light transmission filter 3 and the LED illumination 5 may be in contact with each other or may be separated from each other. The light transmission filter 3 transmits only the light having a specific wavelength corresponding to the spectral transmission characteristic of the light transmission filter 3 by transmitting the outgoing light L1 emitted from the LED illumination 5. That is, the peak wavelength in the spectral characteristics of the transmitted light L2 is the same as the transmittance peak wavelength in the spectral transmission characteristics of the light transmission filter 3. Further, the transmittance peak wavelength in the spectral transmission characteristic of the light transmission filter 3 and the transmittance peak wavelength in the spectral transmission characteristic of the on-chip color filter 21 are the same. Similarly, when the on-chip color filter 21 supports not only visible light but also specific infrared spectrum, the transmittance peak wavelength in the spectral transmission characteristic of the light transmission filter 3 is the spectrum of the on-chip color filter 21. It is the same as the transmittance peak wavelength in the transmission characteristics. Therefore, the peak wavelength in the spectral characteristic of the transmitted light L2 that has passed through the light transmission filter 3 is the same as the transmittance peak wavelength in the spectral transmission characteristic of the on-chip color filter 21 of the imaging sensor 2. Further, since the transmittance peak wavelength in the spectral transmission characteristic of the on-chip color filter 21 is the same as the peak sensitivity wavelength in the spectral sensitivity characteristic of the imaging sensor 2, the peak wavelength in the spectral characteristic of the transmitted light L2 is the imaging sensor 2. It is the same as the peak sensitivity wavelength in the spectral sensitivity characteristics of

  The power supply 4 supplies power required for the operation of the image sensor 2 and the LED illumination 5 to the image sensor 2 and the LED illumination 5. The power supply 4 is connected to the imaging sensor 2 and the LED groups 51 to 53 (LEDs) of the LED illumination 5.

  The LED illumination 5 emits outgoing light L1. The LED illumination 5 includes LED groups 51 to 53. The LED illumination 5 has an LED group 52 having the same peak wavelength as the peak sensitivity wavelength in the spectral sensitivity characteristics of the image sensor 2, and a peak wavelength slightly shifted from the peak wavelength (slightly shorter or longer than the peak wavelength). The LED groups 51 and 53 are formed together. Therefore, a plurality of LED groups 51 to 53 having different peak wavelengths continuously in a wavelength region from a wavelength longer than the sensitivity wavelength of the imaging sensor 2 to a wavelength shorter than the sensitivity wavelength of the imaging sensor 2 are included in the LED illumination 5. Implemented. Here, the LED illumination 5 is configured to include three LED groups, but the LED illumination 5 may include four or more LED groups. The LED groups 51 to 53 have light having a continuous peak wavelength in a wavelength region where the wavelength of the emitted light L <b> 1 to be irradiated is wider than the sensitivity wavelength region of the image sensor 2. When the LED illumination 5 emits the emitted light L1, all of the LED groups 51 to 53 are caused to emit light. As a result, by emitting all the LED groups 51 to 53 each having a different peak wavelength, the LED illumination 5 has a peak wavelength of the emitted light L1 so as to correspond to a wavelength region wider than the sensitivity wavelength region of the image sensor 2. Can be distributed continuously.

  That is, when the temperature around the surveillance camera 1 changes or the temperature of the LED groups 51-53 changes due to the heat generated by the surveillance camera 1, the wavelength of the light emitted from the LED groups 51-53 shifts. However, any one of the LED groups 51 to 53 generates light having a peak wavelength corresponding to the sensitivity wavelength region of the image sensor 2. Then, the emitted light L1 having various wavelengths generated from the LED groups 51 to 53 (light including a peak wavelength corresponding to the sensitivity wavelength region of the imaging sensor 2) is transmitted through the light transmission filter 3 and irradiated to the subject 6. . For this reason, the emitted light L1 that irradiates the subject 6 becomes light corresponding to the spectral sensitivity characteristic of the image sensor 2.

  As described above, the LED illumination 5 can always irradiate the subject 6 with visible light or infrared light having an optimum wavelength with respect to the spectral sensitivity characteristic of the imaging sensor 2 via the light transmission filter 3. Therefore, the surveillance camera 1 can always perform imaging using the LED illumination 5 having a stable wavelength.

  The reason why the LED illumination 5 includes a plurality of LED groups 51 to 53 will be described below.

  The LED illumination 5 has a peak wavelength corresponding to the LED included in the LED illumination 5, and emits light so as to have various spectral characteristics depending on the type of the LED. The imaging sensor 2 has spectral sensitivity characteristics, and the setting of the spectral sensitivity characteristics greatly affects the color reproducibility performance of the monitoring camera 1. That is, when the spectral sensitivity characteristic of the imaging sensor 2 and the spectral characteristic of the light emitted from the LED illumination 5 are optimally adjusted, the monitoring camera 1 can obtain good color reproducibility and sensitivity performance. Specifically, the peak sensitivity wavelength in the spectral sensitivity characteristic of the image sensor 2 is set to be the same as the peak wavelength in the spectral characteristic of the light emitted from the LED illumination 5.

  As shown in FIG. 2, the spectral characteristics of the light emitted from the LED group have temperature dependence, and a shift occurs in the wavelength of light emitted from the LED group due to a change in the temperature around the monitoring camera 1. In other words, when the temperature in the monitoring camera 1 changes, the wavelength of light emitted from the LED group also changes. FIG. 2 is a characteristic diagram showing the relationship between temperature and the wavelength of one LED in the LED group. For example, as shown in FIG. 2, when the temperature in the monitoring camera 1 is T1, the wavelength of light emitted by one LED in the LED group is λ1. When the temperature in the monitoring camera 1 is T2, the wavelength of light emitted by one LED in the LED group is λ2. When the temperature in the monitoring camera 1 is T3, the wavelength of light emitted by one LED of the LED group is λ3. The temperature in the monitoring camera 1 increases in the order of T1, T2, and T3. The wavelengths become longer in the order of λ1, λ2, and λ3. That is, the higher the temperature in the monitoring camera 1, the longer the wavelength of light emitted by one LED in the LED group.

  FIG. 3A is a characteristic diagram showing the spectral sensitivity characteristic of the image sensor 2 before the temperature change in the monitoring camera 1, and FIG. 3B is one LED group before the temperature change in the monitoring camera 1. It is a characteristic view which shows the spectral characteristic of the light irradiated from. 4A is a characteristic diagram showing the spectral sensitivity characteristic of the image sensor 2 after the temperature in the monitoring camera 1 changes, and FIG. 4B shows one characteristic after the temperature in the monitoring camera 1 changes. It is a characteristic view which shows the spectral characteristic of the light irradiated from LED group. In FIG. 3A and FIG. 4A, the horizontal axis represents wavelength (nm) and the vertical axis represents quantum efficiency (%). In FIG. 3B and FIG. 4B, the horizontal axis is the wavelength (nm) and the vertical axis is the radiation intensity (w / sr).

  As shown in FIGS. 3 and 4, the shift in the spectral characteristics of the light emitted from the LED group due to the temperature change in the monitoring camera 1 is caused by the spectral sensitivity characteristics of the image sensor 2 and the spectral of the light emitted from the LED illumination 5. Deviation occurs from the setting of the surveillance camera 1 whose characteristics are optimally adjusted. Further, when the temperature in the monitoring camera 1 is changed before and after the temperature in the monitoring camera 1 is changed, the peak sensitivity wavelength of the image sensor 2 does not change, but the peak wavelength of the LED group changes. That is, when the temperature in the monitoring camera 1 changes, the peak wavelength of the LED group shifts, and the peak wavelength of the LED group deviates from the optimum peak sensitivity wavelength for the image sensor 2.

  As shown in FIGS. 3A and 4A, when the temperature in the monitoring camera 1 is changed before and after the temperature in the monitoring camera 1 is changed, the imaging sensor 2 The peak sensitivity wavelength does not change from α, β, and γ. However, as shown in FIG. 3B and FIG. 4B, the peak wavelengths of the LED groups are α11, β11, and γ11 before the temperature in the surveillance camera 1 changes. After the temperature in the monitoring camera 1 changes, the peak wavelengths of the LED groups are α12, β12, and γ12. The wavelength of α12 is longer than α11, β12 is longer than β11, and γ12 is longer than γ11.

  Therefore, when there is only one LED group, when the temperature in the monitoring camera 1 changes, the wavelength of the light emitted by the LED group changes, and the peak sensitivity wavelength and the LED illumination in the spectral sensitivity characteristic of the image sensor 2 change. 5 is not the same as the peak wavelength in the spectral characteristics of the light irradiated from 5.

(Operation of surveillance camera 1)
Hereinafter, the operation of the monitoring camera 1 will be described.

  The emitted light L1 is emitted from the LED illumination 5. The outgoing light L1 passes through the light transmission filter 3 and is converted into transmitted light L2. The transmitted light L2 converted by the light transmission filter 3 is applied to the subject 6. The reflected light L3 obtained by reflecting the transmitted light L2 on the subject 6 passes through the on-chip color filter 21 and enters the imaging sensor 2. The imaging sensor 2 photoelectrically converts the reflected light L3 and captures it as an image.

(Summary of peak wavelengths of LED groups 51 to 53)
5A is a characteristic diagram showing the spectral sensitivity characteristics of the image sensor 2, FIG. 5B is a characteristic chart showing the spectral transmission characteristics of the light transmission filter 3, and FIG. It is a characteristic view which shows the spectral characteristic of the light irradiated from three LED groups 51-53. In FIG. 5A, the horizontal axis represents wavelength (nm) and the vertical axis represents quantum efficiency (%). In FIG. 5B, the horizontal axis represents wavelength (nm) and the vertical axis represents transmittance (%). In FIG. 5C, the horizontal axis represents wavelength (nm) and the vertical axis represents radiation intensity (w / sr).

  As shown in FIG. 5A, the spectral sensitivity characteristic of the imaging sensor 2 has three peak sensitivity wavelengths α, β, and γ. When light having wavelengths close to the peak sensitivity wavelengths α, β, and γ is incident on the image sensor 2, the image sensor 2 can efficiently detect the light. As shown in FIG. 5B, the spectral transmission characteristic of the light transmission filter 3 has three transmittance peak wavelengths α, β, and γ, similarly to the spectral sensitivity characteristic of the imaging sensor 2. As shown in (c) of FIG. 5, the LED groups 51 to 53 have different peak wavelengths. Specifically, the LED group 51 has three peak wavelengths α1, β1, and γ1. The LED group 52 has three peak wavelengths α2, β2, and γ2. The LED group 53 has three peak wavelengths α3, β3, and γ3. The peak wavelengths α1 and α3 are slightly shifted in wavelength from the peak wavelength α2. Similarly, the peak wavelengths β1 and β3 are slightly shifted from the peak wavelength β2. The peak wavelengths γ1 and γ3 are slightly shifted in wavelength from the peak wavelength γ2. At this time, the wavelengths become shorter in the order of the peak wavelengths α1, α2, and α3. Similarly, the wavelengths become shorter in the order of the peak wavelengths β1, β2, and β3. Further, the wavelengths become shorter in the order of the peak wavelengths γ1, γ2, and γ3. That is, in the order of the LED groups 51, 52, and 53, the wavelength of the peak wavelength of the LEDs being used becomes shorter.

  The LED illumination 5 includes LED groups 51 to 53. Since the different peak wavelengths of the LED groups 51 to 53 overlap, the LED illumination 5 has a peak wavelength in a wide wavelength region. As a result, the LED illumination 5 having continuous peak wavelength light in a wider wavelength region than the spectral transmission characteristic of the on-chip color filter 21 is provided in the surveillance camera 1, so that the LED illumination is caused by the temperature change in the surveillance camera 1. The LED illumination 5 can irradiate the subject 6 with the emitted light L1 having a stable spectrum (the wavelength does not change greatly due to a temperature change) even when the spectral characteristics of the emitted light L1 irradiated by the light 5 change. . That is, the surveillance camera 1 can achieve stable color reproducibility and sensitivity performance. In addition, it is possible to provide good imaging without deterioration in color reproducibility due to temperature changes in the monitoring camera 1.

  FIG. 6 is a characteristic diagram showing the relationship between the temperature and the wavelengths of three LEDs selected one by one from the three LED groups 51 to 53. That is, one LED is selected from the LED group 51, one LED is selected from the LED group 52, and one LED is selected from the LED group 53. As shown in FIG. 6, when one LED of the LED group 51 emits light having a wavelength λ0, the temperature of the LED group 51 is T1. When one LED of the LED group 52 emits light having a wavelength λ0, the temperature of the LED group 52 is T2. When one LED of the LED group 53 emits light having a wavelength λ0, the temperature of the LED group 53 is T3. The temperature increases in the order of T1, T2, and T3. That is, by providing the LED groups 51 to 53 in the LED illumination 5, even if the temperature inside the surveillance camera 1 changes between T1 and T3, the LED illumination 5 emits light close to the wavelength λ0 of the three LEDs. One LED can emit light. Therefore, even if the temperature inside the monitoring camera 1 changes slightly, the monitoring camera 1 does not change much the wavelength distribution of the light emitted by the LED illumination 5 by using all of the LED groups 51 to 53. Can be.

[Embodiment 2]
The following will describe another embodiment of the present invention with reference to FIGS. For convenience of explanation, members having the same functions as those described in the embodiment are given the same reference numerals, and descriptions thereof are omitted.

(Schematic configuration of surveillance camera 1a)
First, a schematic configuration of the monitoring camera 1a according to the second embodiment of the present invention will be described with reference to FIG. FIG. 7A is a block diagram showing the structure of the surveillance camera 1a according to Embodiment 2 of the present invention, and FIG. 7B is an enlarged view of the LED illumination 5a shown in FIG.

  As shown in FIG. 7, the monitoring camera 1 a includes an imaging sensor 2, a power supply 4, an LED illumination 5 a, and a control unit 7.

  The imaging sensor 2 includes an on-chip color filter 21, and the reflected light La2 obtained by reflecting the emitted light La1 from the subject 6 is incident, and the reflected light La2 is photoelectrically converted. The imaging sensor 2 captures the state of the subject 6 captured by the monitoring camera 1a as an image by photoelectrically converting the reflected light La2 of the emitted light La1 reflected by the subject 6. The image sensor 2 is connected to a power source 4, and power necessary for the operation of the image sensor 2 is supplied from the power source 4.

  The on-chip color filter 21 is provided in the imaging sensor 2 on the side where the imaging sensor 2 receives the reflected light La2. The on-chip color filter 21 transmits the reflected light La2 reflected by the subject 6 and the imaging sensor 2 photoelectrically converts the transmitted reflected light La2. The on-chip color filter 21 transmits only the light having a specific wavelength corresponding to the spectral transmission characteristic of the on-chip color filter 21 by transmitting the reflected light La2 reflected by the subject 6 from the emitted light La1. Since the transmittance peak wavelength in the spectral transmission characteristic of the on-chip color filter 21 is the same as the peak sensitivity wavelength in the spectral sensitivity characteristic of the imaging sensor 2, in the spectral characteristic of the reflected light La2 that has passed through the on-chip color filter 21. The peak wavelength is the same as the peak sensitivity wavelength in the spectral sensitivity characteristic of the image sensor 2.

  The power source 4 supplies power necessary for the operation of the image sensor 2 and the control unit 7 to the image sensor 2 and the control unit 7. The power source 4 is connected to the image sensor 2 and the control unit 7.

  The LED illumination 5a emits the emitted light La1. The LED illumination 5a includes LED groups 51-53. The LED groups 51 to 53 indicate the optimal spectrum at the temperature in the monitoring camera 1a (measured temperature of the temperature sensors 81 to 83 when the LED groups 51 to 53 are turned off). Is connected to the control unit 7 to select and operate the switching.

  The LED groups 51 to 53 are provided in order to correspond to a wavelength region where the wavelength of the emitted light La <b> 1 to be irradiated is wider than the sensitivity wavelength region of the imaging sensor 2. Further, by providing the LED illumination 51a with the LED groups 51 to 53 having different peak wavelengths, the emitted light La1 emitted by the LED illumination 5a has light having a continuous peak wavelength in a wide wavelength region. That is, the LED groups 51 to 53 have light having a continuous peak wavelength in a wavelength region wider than the sensitivity wavelength region of the imaging sensor 2. The LED illumination 5a includes temperature sensors 81-83. The temperature sensor 81 measures the temperature of the LED group 51. The temperature sensor 82 measures the temperature of the LED group 52. The temperature sensor 83 measures the temperature of the LED group 53. Further, each of the temperature sensors 81 to 83 is connected to the power source 4. The temperature sensor 81 is provided in the vicinity of the LED group 51, the temperature sensor 82 is provided in the vicinity of the LED group 52, and the temperature sensor 83 is provided in the vicinity of the LED group 53.

  The control unit 7 is connected to the LED groups 51 to 53 and is connected to the temperature sensors 81 to 83. The control unit 7 is connected to the power source 4. The control unit 7 can operate the LED groups 51 to 53 separately, and selects the operation of the LED groups 51 to 53 by switching. Based on the temperature measured by the temperature sensors 81 to 83, the control unit 7 has the LED group 51 having light having a wavelength closest to the peak sensitivity wavelength in the spectral sensitivity characteristics of the imaging sensor 2 among the LED groups 51 to 53. The LED group of any one of -53 is selected and operated. Specifically, the control unit 7 determines which of the optimum temperature T1 of the LED group 51, the optimum temperature T2 of the LED group 52, and the optimum temperature T3 of the LED group 53 is the temperature inside the monitoring camera 1a. . The optimum temperature is a temperature at which the peak wavelength in the spectral characteristics of the light emitted from the LED group is the same as the peak sensitivity wavelength in the spectral sensitivity characteristics of the image sensor 2. Since the peak wavelength of the LED groups 51 to 53 shifts due to a change in temperature, a memory (not shown) in the control unit 7 is preliminarily operated so as to operate a specific LED group having optimum characteristics with respect to a specific temperature. The optimum temperatures T1 to T3 of the LED groups 51 to 53 are set. First, the control part 7 detects the temperature in the monitoring camera 1a when the LED groups 51-53 are extinguished by the temperature sensors 81-83. When one of the LED groups 51 to 53 is operating, the temperature in the monitoring camera 1a is detected by a temperature sensor that measures the temperature of the operating LED group. Next, the control unit 7 compares the temperature in the monitoring camera 1a with the optimum temperatures T1 to T3 of the LED groups 51 to 53 recorded in the memory in the control unit 7 to obtain the optimum temperatures T1 to T3. Among them, it is determined which is closest to the temperature in the monitoring camera 1a. And the control part 7 selects and operates the LED group which has the optimal temperature nearest to the temperature in the monitoring camera 1a. As a result, the LED illumination 5 always selects the LED group having the optimum peak wavelength by the control unit 7, so that the spectral sensitivity of the image sensor 2 is always applied to the subject 6 even if the temperature in the monitoring camera 1 a changes. It is possible to irradiate visible light or infrared light having an optimum wavelength for the characteristics. Therefore, the surveillance camera 1a can always perform imaging using the LED illumination 5 having a stable wavelength.

  As shown in FIG. 7B, the LED group 51 includes LEDs 511-513. The LED group 52 includes LEDs 521 to 523. The LED group 53 includes LEDs 531 to 533. Each of the LEDs 511, 521, and 531 is a blue LED, each of the LEDs 512, 522, and 532 is a green LED, and each of the LEDs 513, 523, and 533 is a red LED. As described above, the LED groups 51 to 53 use LEDs of three colors (blue, green, and red), and the LED groups 51 to 53 can emit light suitable for the spectral transmission characteristics of the on-chip color filter 21. it can.

  Next, spectral sensitivity characteristics of the image sensor 2 and spectral characteristics of light emitted from the LED groups 51 to 53 will be described with reference to FIG. FIG. 8A is a characteristic diagram showing the spectral sensitivity characteristic of the image sensor 2. 8B is a characteristic diagram showing the spectral characteristics of the light emitted from the LED group 51, and FIG. 8C is a characteristic chart showing the spectral characteristics of the light emitted from the LED group 52. FIG. 8D is a characteristic diagram showing the spectral characteristics of the light emitted from the LED group 53. In FIG. 8A, the horizontal axis represents wavelength (nm) and the vertical axis represents quantum efficiency (%). 8B to 8C, the horizontal axis represents wavelength (nm) and the vertical axis represents radiation intensity (w / sr).

  As shown in FIG. 8A, the spectral sensitivity characteristic of the imaging sensor 2 has three peak sensitivity wavelengths α, β, and γ. FIG. 8B is a characteristic diagram showing the spectral characteristics of light emitted from the LED group 51 when the control unit 7 selects and operates the LED group 51 (the solid line is operating). This is the spectral characteristic of the light emitted from the LED group 51, and the dotted line is the spectral characteristic of the light emitted from the LED groups 52 and 53 that are not operating). As shown in FIG. 8B, the spectral characteristics of the light emitted from the LED group 51 have three peak wavelengths α1, β1, and γ1. FIG. 8C is a characteristic diagram showing the spectral characteristics of the light emitted from the LED group 52 when the control unit 7 selects and operates the LED group 52 (the LED group in which the solid line is operating). 52 is a spectral characteristic of light emitted from the LED group, and is a spectral characteristic of light emitted from the LED group in which the dotted line is not operating). As shown in FIG. 8C, the spectral characteristic of the light emitted from the LED group 52 has three peak wavelengths α2, β2, and γ2. FIG. 8D is a characteristic diagram showing the spectral characteristics of the light emitted from the LED group 53 when the control unit 7 selects and operates the LED group 53 (the LED group in which the solid line is operating). 53 is a spectral characteristic of light emitted from the LED group 51, and a dotted line is a spectral characteristic of light emitted from the LED groups 51 and 52 that are not operating. As shown in FIG. 8D, the spectral characteristics of the light emitted from the LED group 53 have three peak wavelengths α3, β3, and γ3. The peak wavelengths α1 and α3 are slightly shifted in wavelength from the peak wavelength α2. Similarly, the peak wavelengths β1 and β3 are slightly shifted from the peak wavelength β2. The peak wavelengths γ1 and γ3 are slightly shifted in wavelength from the peak wavelength γ2. At this time, the peak wavelengths become shorter in the order of α1, α2, and α3. Similarly, the peak wavelengths become shorter in the order of β1, β2, and β3. The peak wavelengths are shorter in the order of γ1, γ2, and γ3. In other words, the peak wavelength of the LEDs used decreases in the order of the LED groups 51, 52, and 53.

  The control unit 7 changes the operation of the LED group according to the temperature in the monitoring camera 1a. Specifically, if the temperature in the monitoring camera 1a is closest to T1 among T1 to T3, the LED group 51 is selected and operated. If the temperature in the monitoring camera 1a is closest to T2 among T1 to T3, the LED group 52 is selected and operated. If the temperature in the monitoring camera 1a is closest to T3 among T1 to T3, the LED group 53 is selected and operated. As a result, the subject 6 can always be irradiated with the optimum emission light La1 by changing the operation of the LED group according to the preset operating conditions.

(Operation of surveillance camera 1a)
Below, operation | movement of the surveillance camera 1a is demonstrated.

  The control unit 7 selects and operates the LED group according to the temperature in the monitoring camera 1a. The emitted light La1 is emitted from the LED illumination 5a. The emitted light La1 is applied to the subject 6. The reflected light La2 obtained by reflecting the emitted light La1 on the subject 6 passes through the on-chip color filter 21 and enters the imaging sensor 2. The imaging sensor 2 photoelectrically converts the reflected light La2 and captures it as an image.

[Embodiment 3]
The following will describe another embodiment of the present invention. For convenience of explanation, members having the same functions as those described in the embodiment are given the same reference numerals, and descriptions thereof are omitted.

  In the surveillance camera 1b according to the third embodiment, fine adjustment of white balance using a lookup table will be described below.

  A plurality of LED groups corresponding to various operating conditions (such as optimum temperatures T1 to T3 of the LED groups 51 to 53) set in advance in a memory (not shown) in the control unit 7a are provided in the LED illumination 5a. Assuming that there are N types of LED groups and the temperature range assumed is T ° C. to T + ΔT ° C., the LED temperature steps are ΔT / N when the LED temperature steps at which the operating LED groups are switched are set uniformly. The LED temperature step indicates how many temperature ranges the LED group is switched over. That is, depending on the temperature of the LED group, the LED group is operated at a temperature setting that is shifted by ΔT / 2N at the maximum from the optimum temperature of the LED group.

  In addition, when there are many types of LED groups (when N is large) and the surveillance camera 1b is operated in a narrow temperature range (when ΔT is small), since the LED temperature step is fine, a more optimal LED group is operated. be able to. When the type of LED group is small (when N is small) and the surveillance camera 1b is operated in a wide temperature range (when ΔT is large), the LED group is operated at a temperature setting with a large deviation from the optimum temperature of the LED group. I will let you. Therefore, a deviation from the optimum temperature of the LED group causes a deviation from the wavelength of the optimum LED group, and a deviation from the optimum white balance set in the monitoring camera 1b. However, the deviation from the white balance is a deviation that can be corrected by fine adjustment. This is because, as described in the second embodiment, the control unit 7 selects and operates the optimum LED group as much as possible.

  Here, fine adjustment of the white balance is performed by the following method. A look-up table in which the temperature difference d between the temperature of the LED group actually operating and the optimum temperature of the LED group is associated with the parameter f (d) for adjusting the white balance, 7 is stored in a memory (not shown). As described in the second embodiment, the monitoring camera 1b is operated, and the control unit 7 selects and operates the optimum LED group as much as possible. Among the temperature sensors 81 to 83, the temperature sensor corresponding to the LED group that is actually operating measures the temperature of the LED group that is actually operating, and is actually set to the optimum temperature of the LED group that is set in advance. A temperature difference d from the temperature of the LED group in operation is detected. The control unit 7 obtains a white balance parameter f (d) from the value of the temperature difference d according to a lookup table.

  The lookup table can be set, for example, like the lookup table shown in Table 1 below.

  In the look-up table shown in Table 1, when the temperature is 3 ° C. to 5 ° C. lower than the optimum temperature of the LED group, the white balance parameter f (d) is [x1 (R gain), y1 (G gain), z1 (B gain). )]. When the temperature is higher by 3 ° C. to 5 ° C. than the optimum temperature of the LED group, [x2 (R gain), y2 (G gain), z2 (B gain)] is used as the white balance parameter f (d).

  Regarding [x1 (R gain), y1 (G gain), z1 (B gain)], the values of R gain, G gain, and B gain are the peak wavelength, temperature, and imaging center 2 of the LED groups 51-53. The peak sensitivity wavelength is calculated and stored in a lookup table. The same applies to [x2 (R gain), y2 (G gain), z2 (B gain)].

  Therefore, the control unit 7 performs fine adjustment of the white balance of the monitoring camera 1b based on the temperature difference d and the parameter f (d) of the lookup table. Thereby, further improvement in image quality of the surveillance camera 1b can be realized.

[Summary]
The surveillance camera 1 according to the first aspect of the present invention is arranged so as to face the LED illumination 5 that irradiates the emitted light L1, and a filter that converts only the emitted light L1 having a specific wavelength into transmitted light L2. (Light transmission filter 3) and an imaging sensor 2 that photoelectrically converts the reflected light L3 of the transmitted light L2 reflected by the subject 6, and the LED illumination 5 is wider than the sensitivity wavelength region of the imaging sensor 2. A plurality of LEDs (LED groups 51 to 53) are provided so as to have light having a continuous peak wavelength in the wavelength region, and the peak wavelength in the spectral characteristic of the transmitted light L2 is the peak in the spectral sensitivity characteristic of the image sensor 2. It is the same as the sensitivity wavelength.

  According to said structure, LED illumination is equipped with several LED so that the wavelength of an emitted light may correspond to a wavelength range wider than the sensitivity wavelength of an image sensor, and LED illumination is wider than the sensitivity wavelength range of an image sensor. The peak wavelength of the emitted light can be continuously distributed so as to correspond to the wavelength region.

  Therefore, the surveillance camera can realize stable color reproducibility and sensitivity performance. In addition, since the wavelength of the emitted light corresponds to a wavelength range wider than the sensitivity wavelength range of the imaging sensor, it is possible to provide good imaging without deterioration of color reproducibility due to a temperature change in the monitoring camera.

  Therefore, even if the temperature around the surveillance camera changes, there is an effect of realizing a surveillance camera capable of obtaining good imaging.

  The surveillance camera 1a according to the aspect 2 of the present invention receives the LED illumination 5a that irradiates the emitted light La1 and the reflected light La2 that is reflected from the subject 6 and photoelectrically converts the reflected light La2. The imaging sensor 2 and a plurality of LEDs (LED groups 51 to 53) provided in the LED illumination 5a are selected so as to have continuous peak wavelength light in a wavelength range wider than the sensitivity wavelength range of the imaging sensor 2. And the LED illumination 5a includes a plurality of temperature sensors 81 to 83 for measuring the temperatures of the plurality of LEDs (LED groups 51 to 53), and the control unit 7 includes Based on the temperature measured by the plurality of temperature sensors 81 to 83, the peak in the spectral sensitivity characteristic of the imaging sensor 2 among the plurality of LEDs (LED groups 51 to 53). And wherein the operating Select only the 1LED an LED having a light wavelength nearest to the sensitivity wavelength.

  According to the above configuration, the LED illumination is always selected by the control unit with the LED group having the optimum peak wavelength, so that visible light or infrared light having the optimum wavelength for the spectral sensitivity characteristic of the imaging sensor is always applied to the subject. Can be irradiated. Therefore, the surveillance camera can always take an image using LED illumination having a stable wavelength.

  In addition, by changing the operation of the LED group according to preset operation conditions, it is possible to always irradiate the subject with the optimum emitted light.

  Therefore, even if the temperature around the surveillance camera changes, there is an effect of realizing a surveillance camera capable of obtaining good imaging.

  The surveillance camera 1 according to aspect 3 of the present invention is the on-chip color filter according to aspect 1, wherein the imaging sensor 2 transmits only the reflected light L3 having the same wavelength as the peak wavelength in the spectral characteristics of the transmitted light L2. May be provided.

  According to the above configuration, since the transmittance peak wavelength in the spectral transmission characteristic of the on-chip color filter is the same as the peak sensitivity wavelength in the spectral sensitivity characteristic of the imaging sensor, the reflected light L3 transmitted through the on-chip color filter. The peak wavelength in the spectral characteristic is the same as the peak sensitivity wavelength in the spectral sensitivity characteristic of the imaging sensor. Thereby, since the image sensor receives the reflected light L3 having the same wavelength as the peak sensitivity wavelength in the spectral sensitivity characteristic of the image sensor, the surveillance camera can obtain a good image.

  The surveillance camera 1a according to aspect 4 of the present invention is the first temperature which is one of the plurality of temperature sensors 81 to 83 in which the control unit 7 measures the temperature of the first LED. With reference to a look-up table showing the relationship between the temperature difference d and the parameter f (d) for finely adjusting the white balance in the temperature difference d between the temperature measured by the sensor and the optimum temperature of the first LED. The white balance may be finely adjusted according to the temperature difference d and the lookup table.

  According to said structure, the further image quality improvement of a surveillance camera is realizable.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention. Furthermore, a new technical feature can be formed by combining the technical means disclosed in each embodiment.

1 ・ 1a ・ 1b Surveillance camera 2 Imaging sensor 3 Light transmission filter
4 Power supply 5 · 5a LED lighting 6 Subject 7 · 7a Control unit 21 On-chip color filter 51 · 52 · 53 LED group (LED)
81 ・ 82 ・ 83 Temperature sensor 511 ・ 512 ・ 513 ・ 521 ・
522, 523, 531, 532, 533 LED
L1 outgoing light L2 transmitted light L3 reflected light La1 outgoing light La2 reflected light

Claims (4)

LED illumination for irradiating emitted light;
A filter that is arranged to face the LED illumination and converts only the emitted light of a specific wavelength into transmitted light;
An imaging sensor that photoelectrically converts the reflected light of the transmitted light reflected by the subject;
The LED illumination includes a plurality of LEDs so as to have continuous peak wavelength light in a wavelength region wider than the sensitivity wavelength region of the imaging sensor,
The monitoring camera, wherein a peak wavelength in the spectral characteristic of the transmitted light is the same as a peak sensitivity wavelength in the spectral sensitivity characteristic of the imaging sensor. LED illumination for irradiating emitted light;
An imaging sensor that receives reflected light obtained by reflecting the emitted light from a subject and photoelectrically converts the reflected light; and
A control unit that selects and operates a plurality of LEDs provided in the LED illumination so as to have continuous peak wavelength light in a wavelength region wider than the sensitivity wavelength region of the imaging sensor;
The LED illumination includes a plurality of temperature sensors that measure the temperature of each of the plurality of LEDs,
The control unit is a first LED that has light having a wavelength closest to a peak sensitivity wavelength in a spectral sensitivity characteristic of the imaging sensor among the plurality of LEDs based on temperatures measured by the plurality of temperature sensors. Surveillance camera characterized by selecting only to operate.   The surveillance camera according to claim 1, wherein the imaging sensor includes an on-chip color filter that transmits only the reflected light having the same wavelength as the peak wavelength in the spectral characteristics of the transmitted light. The control unit measures a temperature of the first LED, and a temperature difference between a temperature measured by a first temperature sensor that is one of the plurality of temperature sensors and an optimum temperature of the first LED, Refer to the lookup table that shows the relationship between the temperature difference and the parameters for fine adjustment of the white balance.
The surveillance camera according to claim 2, wherein the white balance is finely adjusted according to the temperature difference and the lookup table.

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