JP5655441B2 - Image sensor, imaging device using the image sensor, and in-vehicle monitoring device using the imaging device - Google Patents

Description

  The present invention relates to an image sensor, an in-vehicle camera as an imaging device using the image sensor, and an in-vehicle monitoring device using the imaging device.

  In recent years, in order to reduce the blind spot of a driver, a camera as an imaging device is installed in the rear part of an automobile or the like, an outside mirror, etc., and an image taken by this camera is displayed on a monitor installed in the vehicle. Monitoring devices have been put into practical use as products.

When shooting outdoors during the daytime with this type of in-vehicle camera, sufficient illuminance is obtained and the video is good, so the quality of the captured image is rarely regarded as a problem.
On the other hand, for shooting at night with this type of in-vehicle camera, images are often taken under the illuminance condition below the minimum illuminance that can be imaged with the in-vehicle camera. Even if the video from the in-vehicle camera is displayed on the monitor, the driver cannot determine what is shown.

  Some in-vehicle monitoring devices have an in-vehicle camera installed at the rear end of the vehicle to visually recognize the rear of the vehicle. In this type of in-vehicle monitoring device, since the back lamp of the vehicle is used as an illumination light source, a certain level of illuminance can be obtained even at night in the area illuminated by the illumination light source, and the quality of the captured image is a problem. There is little to be done.

  On the other hand, there is also a vehicle-mounted monitoring device that monitors the blind spot on the side surface of the vehicle body on the passenger seat side by installing a vehicle-mounted camera on the outside mirror on the passenger seat side instead of behind the vehicle. In this in-vehicle monitoring device, since there are usually many vehicles that are not provided with an illumination light source in the vicinity of the outside mirror, when the vehicle is traveling at night and on a road where there is no street light, the image is taken with an in-vehicle camera. Even if the video is displayed on the monitor, nothing appears to be shown.

Therefore, in this in-vehicle monitoring device, there is a problem that the blind spot on the passenger seat side cannot be visually recognized under the above conditions.
Therefore, in order to solve this problem, an in-vehicle camera with a configuration in which an infrared illumination light source is incorporated into the in-vehicle camera so that the blind spot area can be viewed on the monitor even under shooting environment conditions that are difficult to see at night. Monitoring devices are already known.

  The reason for using infrared light is that if visible light is used, people around it may be dazzled, and image sensors that are usually used in in-vehicle cameras are also sensitive to the near infrared region. It is because it has.

  This in-vehicle monitoring device using an in-vehicle camera with an infrared illumination light source is not included in sunlight because there is no infrared light cut filter that cuts infrared light to guide infrared light to the image sensor. Infrared light is also received by the image sensor, and there is a problem that color reproducibility during daytime shooting deteriorates.

  As a similar technique, a camera is configured by an auxiliary light source for invisible light, an image sensor (an image sensor or a collection of photoelectric conversion elements), and an optical filter provided in front of the image sensor, and the optical filter Some of them are known to have a characteristic of transmitting part of visible light and invisible light and cutting part of the invisible light (see Patent Document 1).

This has the problem that it is difficult to improve the color reproducibility during daytime photography.
A camera having a configuration in which an optical filter that selectively transmits a part of infrared light is provided in front of an image sensor is also known (see Patent Document 2 and Patent Document 3).

  These cameras are also aimed at improving the color reproducibility at the same time that it is possible to take good images at night with an illumination light source in the infrared region. Sometimes, the hue is still poor, and the color of the leaf that should be green is displayed in white on the monitor, which makes it difficult for the driver to determine at a glance what is displayed.

  Further, the first to third photoelectric conversion elements provided with three color filters of a normal color camera for the purpose of providing good color reproducibility without providing an infrared light cut filter in the imaging device (camera). In addition, a color imaging device using this image sensor is also known in which an image sensor is configured by providing a fourth photoelectric conversion element that photoelectrically converts infrared light and outputs a signal component corresponding to the infrared light. (See Patent Document 4).

  In the one disclosed in Patent Document 4, red light obtained by a fourth photoelectric conversion element from RGB signals of visible light including signal components corresponding to infrared light obtained by the first to third photoelectric conversion elements. A signal component corresponding to external light is removed by signal processing, thereby improving the color reproducibility of the color image.

  However, in the device disclosed in Patent Document 4, color reproducibility can be improved by devising the photoelectric conversion element and filter of the image sensor, but the fourth photoelectric device having sensitivity only in the infrared region. There is a problem that the sensitivity is lower than that of the conventional image sensor by the amount of the conversion element.

  That is, in a conventional on-vehicle monitoring device, in order to improve color reproducibility during daytime shooting, for example, an infrared light cut filter that cuts light from a wavelength of 700 nm to a wavelength of 850 nm is used for an image sensor. The color reproducibility is somewhat improved by using an infrared illumination light source that is provided in front and generates infrared light in the wavelength range from 850 nanometers to 1000 nanometers. As for the leaves, the color still remains bad during daytime shooting, and the color of the leaves, which should be green, is displayed on the monitor in white, and it is difficult for the driver to determine at a glance what is displayed. .

  On the other hand, the signal component corresponding to the infrared light obtained by the fourth photoelectric conversion element from the RGB signal of visible light including the signal component corresponding to the infrared light obtained by the first to third photoelectric conversion elements. In a color imaging device that removes the signal by signal processing, the sensitivity is lower than that of a conventional image sensor.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to assemble an infrared illumination light source into an imaging apparatus and to detect a blind spot area on a monitor even under shooting environment conditions that are difficult to see at night. An in-vehicle monitoring device configured to be visually recognized includes an image sensor capable of improving the reproducibility of the color of leaves outdoors during daytime shooting, an imaging device using the image sensor, and the imaging device. The object is to provide an in-vehicle monitoring device.

The image sensor according to claim 1, a plurality of pixels having sensitivity to light in a wavelength region from a visible region to an infrared region;
The red wavelength region is provided in front of at least one of the plurality of pixels and transmits visible light in a blue wavelength region, and the red wavelength region in visible light and infrared wavelength regions in a green wavelength region and a red wavelength region. A first optical filter that cuts infrared light on a longer wavelength side and shorter wavelength region side than a specific wavelength and transmits infrared light on a longer wavelength side than the specific wavelength;
Visible light in the red wavelength region and visible light in the blue wavelength region and the green wavelength region are provided in front of one or more pixels in which the first optical filter is not provided among the plurality of pixels. In the infrared wavelength region, infrared light that is longer than the red wavelength region and shorter than the specific wavelength is cut, and infrared light that is longer than the specific wavelength is transmitted. A second optical filter;
Among the plurality of pixels, the first optical filter and the second optical filter that are not provided are provided in front of one or more pixels to transmit visible light in the green wavelength region and the blue wavelength region, And a third optical filter that cuts visible light in the red wavelength region and transmits infrared light having a longer wavelength than the red wavelength region.

The image sensor according to claim 2, wherein the first optical filter transmits visible light in the blue wavelength region, cuts visible light in the green wavelength region and the red wavelength region, and is longer than the red wavelength region. A blue filter that transmits infrared light on the wavelength side and an infrared light cut filter that cuts light on the shorter wavelength side than the specified wavelength and transmits infrared light on the longer wavelength side than the specified wavelength are superimposed. Configured
The second optical filter transmits red light in the red wavelength region, cuts visible light in the blue wavelength region and the green wavelength region, and transmits infrared light on a longer wavelength side than the red wavelength region. A filter and an infrared light cut filter that cuts light on a shorter wavelength side than the specific wavelength and transmits infrared light on a longer wavelength side than the specific wavelength are overlapped,
The third optical filter transmits green light in the green wavelength region, cuts visible light in the blue wavelength region and the red wavelength region, and transmits infrared light on a longer wavelength side than the red wavelength region. It is characterized by comprising a filter.

The image sensor according to claim 3 is characterized in that the specific wavelength is set in the vicinity of a limit of an upper limit wavelength of a wavelength region of a reflection characteristic of a leaf of a plant.
The image sensor according to claim 4 is characterized in that the specific wavelength is a wavelength in the vicinity of 900 nm.

An imaging apparatus according to a fifth aspect includes an image sensor according to any one of the first to fourth aspects, a signal processing circuit unit that processes a video signal output from the image sensor, and an imaging target region. An illumination light source circuit unit that illuminates the image sensor, the signal processing circuit unit, and a control circuit unit that controls the illumination light source circuit unit, wherein the illumination light source circuit unit is on a longer wavelength side than the specific wavelength. A light emitting source having a light emitting characteristic is provided.
The imaging device according to claim 6 is characterized in that the light emitting source is an infrared light emitting diode.
The on-vehicle monitoring device according to claim 7 controls the imaging device provided in the vehicle, the monitor provided in the vehicle, and the imaging device according to claim 5 or 6 provided in the vehicle. It is characterized by comprising an external control device.

  When an in-vehicle monitoring apparatus is configured using an imaging apparatus using an image sensor according to the present invention, it is possible to improve the reproducibility of the color of the leaves of an outdoor tree during daytime shooting. Further, even when an infrared light emitting diode is used as the light emitting source, the unnatural color at the time of night photographing can be eliminated.

  This is because if the specific wavelength is set in the vicinity of the upper limit of the reflection intensity characteristic of the leaf of the plant, the first optical element that transmits the light in the blue wavelength region and the light in the red wavelength region are transmitted. A pixel provided with two optical elements is only a pixel provided with a third optical element that is not sensitive to infrared light reflected from the leaves of a plant and transmits light in the green wavelength region. Is sensitive to infrared light reflected from the leaves of the plant, so that when a plant leaf is imaged, the G signal is output only from the pixel provided with the third optical element, and the signal processing circuit unit This is because it is processed as a green signal and output and displayed on the monitor.

  In addition, if a light emitting source having a light emission characteristic in a wavelength region above a specific wavelength is used, each pixel has equivalent sensitivity to infrared light in the wavelength region above the specific wavelength even during night photography. Therefore, it is possible to eliminate the unnaturalness of color during night shooting.

FIG. 1 is a block circuit diagram showing a schematic configuration of an in-vehicle monitoring apparatus according to an embodiment of the present invention. FIG. 2 is an external view of the in-vehicle camera as the imaging apparatus shown in FIG. FIG. 3 is an explanatory view showing a state in which the outside mirror device to which the in-vehicle camera shown in FIG. 2 is attached is viewed from below. 4 is a detailed circuit diagram of the illumination light source circuit unit shown in FIG. FIG. 5 is a graph showing the light emission characteristics of the infrared light emitting diode shown in FIG. FIG. 6 is a schematic diagram showing an example of the image sensor shown in FIG. FIG. 7 is a cross-sectional view taken along the line AA of the image sensor shown in FIG. 8 is a cross-sectional view of the image sensor shown in FIG. 6 taken along line BB. FIG. 9 is a graph showing the transmittance characteristics of the RGB filter shown in FIG. FIG. 10 is a graph showing the transmittance characteristics of the infrared cut filter shown in FIG. FIG. 11 is a graph showing sensitivity distribution characteristics of a conventional image sensor. FIG. 12 is a graph showing the intensity distribution of the reflected light of the leaves of the plant. FIG. 13 is a graph showing sensitivity distribution characteristics of the image sensor according to the present invention. FIG. 14 is a plan view showing a vehicle to which the in-vehicle camera shown in FIG. 3 is attached.

FIG. 1 is a block circuit diagram showing a schematic configuration of an in-vehicle monitoring apparatus according to an embodiment of the present invention. This in-vehicle monitoring device is generally composed of an in-vehicle camera 1 as an imaging device, a monitor 2 and an external control device 3.
The in-vehicle camera 1 includes an imaging lens 4, an illumination lens 5, an image sensor 6, a signal processing circuit unit 7, and an illumination light source circuit unit 8, and includes these image sensor 6, signal processing circuit unit 7, and illumination light source circuit unit 8. A control circuit unit 9 for controlling is provided.

These imaging lens 4, illumination lens 5, image sensor 6, signal processing circuit unit 7, and control circuit unit 9 are arranged inside a housing 10 shown in FIG. The harness 11 is pulled out from the housing 10, and the harness 11 is connected to the monitor 2 and the external control device 3.
The camera unit 12 includes the imaging lens 4, the image sensor 6, and the signal processing circuit unit 7, and the illumination unit 13 includes the illumination lens 5 and the illumination light source circuit unit 8.

  The in-vehicle camera 1 is disposed on the lower surface of the outside mirror device 14 as shown in FIG. Reference numeral 15 denotes a part of a vehicle body side portion to which the outside mirror device is attached. Here, it is assumed that the in-vehicle camera 1 is attached to the outside mirror device 14 on the side close to the passenger seat on the side opposite to the outside mirror on the side close to the driver seat.

The illumination unit 13 illuminates the imaging target region, and the camera unit 12 captures the imaging target region illuminated by the illumination unit 13 when traveling at night.
For example, a wide-angle lens is used as the imaging lens 4. An imaging target existing in the imaging target region is imaged on the image sensor 6 by the imaging lens 4. The image sensor 6 photoelectrically converts the light image formed on the light receiving surface and outputs it as a video signal to the signal processing circuit unit 7.

The image sensor 6 uses an image sensor such as a CCD or CMOS which has sensitivity mainly in the visible light region and slightly sensitivity in the infrared light region. In other words, the imaging element (pixel) has a sensitivity for photoelectric conversion in a wavelength region from the visible light region to the infrared light region.
The signal processing circuit unit 7 converts the video signal output from the image sensor 6 into a signal of a predetermined system such as an NTSC signal. The video signal converted into the predetermined method is input to the monitor 2 via the harness 11.

The external control device 3 performs on / off control of the image sensor 6, the signal processing circuit unit 7, and the illumination light source circuit unit 8 via the control circuit unit 9.
As shown in FIG. 4, the illumination light source circuit unit 8 includes, for example, a constant current source 16, an infrared light emitting diode (LED) 17 as a light emission source, and an N-channel field effect transistor (FET) 18. . The anode of the infrared light emitting diode 17 is connected to the constant current source 16, and the cathode of the infrared light emitting diode 17 is connected to the drain of the N-channel field effect transistor 18. The source of the N-channel field effect transistor 18 is grounded.

  A high-level or low-level control signal is input from the control circuit unit 9 to the gate of the N-channel field effect transistor 18 via the input terminal 19. The N-channel field effect transistor 18 is ON / OFF controlled by the control circuit unit 9, and the N-channel field effect transistor 18 is turned ON when a high level signal is input to its gate, thereby turning on the infrared light emitting diode 17. The The N-channel field effect transistor 18 is turned off when a low level signal is input to the gate thereof, whereby the infrared light emitting diode 17 is turned off.

Infrared light emitted from the infrared light emitting diode 17 is collected by the illumination lens 5, and the infrared light collected by the illumination lens 5 is uniformly irradiated toward the imaging target region.
As the infrared light emitting diode 17, as shown in FIG. 5, a diode having a light emission characteristic Q1 having a light emission wavelength region of 900 nm to 1000 nm and a light emission intensity peak in the vicinity of 950 nm is used. The reason will be described later.

  Note that a luminance value determination circuit (not shown) is provided in the signal processing circuit unit 7, a luminance value is obtained based on the video signal output from the image sensor 6 by the luminance value determination circuit, and an imaging target region is based on the luminance value. When the brightness value is determined to be lower than a predetermined threshold using the brightness value determination circuit, it is determined that the shooting environment around the automobile is dark, and the illumination light source circuit unit 8 A control signal for turning on the light emitting diode 17 may be output to the control circuit unit 9 to turn on the infrared light emitting diode 17.

Further, instead of obtaining the luminance value based on the video signal, the lighting of the infrared light emitting diode 17 may be controlled by detecting the brightness in the vicinity of the imaging target region using a photometric sensor such as a photodiode or a photoresistor. it can.
Each pixel as each photoelectric conversion element of the image sensor 6 according to this embodiment is sensitive to light having a wavelength in the visible region (400 nm to 700 nm) and is sensitive to light having a wavelength in the infrared region (700 nm to 1000 nm). It also has sensitivity.

  6 to 8 show an example of an imaging unit of an image sensor as the image sensor 6. In FIG. 6, 20 is each pixel as an image sensor (image element), and 21 is R (optical filter). A red (red) filter, 22 is a G (green) filter as an optical filter, 23 is a B (blue) filter as an optical filter, 24 is a vertical transfer register, 25 is a horizontal transfer register, and 26 is an output circuit unit. Each pixel 20 is arranged in a matrix, and an optical filter is provided in front of each pixel 20. Each pixel 20 is constituted by a photoelectric conversion element such as a silicon photodiode. Further, the vertical transfer register 24 and the horizontal transfer register 25 are also composed of an image sensor (CCD).

The R filter 21, G filter 22, and B filter 23 have the transmittance characteristics shown in FIG. The B filter 23 has a transmittance peak in the vicinity of a wavelength of 450 nm, and has a characteristic Q2 that transmits blue light in a range of approximately 400 nm to 550 nm and infrared light having a wavelength of 700 nm or more.
The G filter 22 has a transmittance peak in the vicinity of a wavelength of 550 nm, and has a characteristic Q3 that transmits green light within a wavelength range of approximately 450 nm to 650 nm and infrared light having a wavelength of 700 nm or more.

The R filter 21 has a peak in the vicinity of a wavelength of 650 nm, and has a characteristic Q4 that transmits red light within a wavelength range of approximately 650 nm to 700 nm and infrared light having a wavelength of 700 nm or more.
These color filters are arranged in each pixel 20 by an arrangement method called a Bayer arrangement. In front of the R filter 21 and the B filter 23, an infrared light cut filter 27 for cutting infrared light is provided as shown in FIGS. As shown in FIG. 10, the infrared light cut filter 27 has a general characteristic Q5 whose cutoff wavelength (specific wavelength) is in the vicinity of 900 nm.

Each pixel 20 is coupled to a vertical transfer register 24, and each charge generated based on photoelectric conversion for each pixel 20 is transferred as a current signal in the vertical direction based on a vertical transfer clock signal, and guided to the horizontal transfer register 25. The charges transferred to the horizontal transfer register 25 are transferred in the horizontal direction based on the horizontal transfer clock signal and input to the output circuit unit 26. The output circuit unit 26 converts the current signal into a voltage signal. The voltage signal is input to the signal processing circuit unit 7 at the subsequent stage.
As a result, a color signal corresponding to the color of the color filter is output from each pixel 20 to the signal processing circuit unit 7.

  In this embodiment, the visible light in the blue wavelength region is provided in front of at least one of the plurality of pixels 20 having sensitivity to light in the wavelength region from the visible region to the infrared region. The B filter 23 to be transmitted and the infrared light cut filter 27 are overlapped so that the visible wavelength and the infrared wavelength region in the green wavelength region and the red wavelength region are longer than the red wavelength region and have a specific wavelength (900 nm). A first optical filter that cuts infrared light on the shorter wavelength region side and transmits infrared light on the longer wavelength side than the specific wavelength is configured.

  An R filter 21 that is provided in front of one or more pixels 20 that are not provided with the first optical filter among the plurality of pixels 20 and transmits visible light in the red wavelength region and an infrared light cut filter 27 are overlapped. Among the visible light and the infrared wavelength region in the blue wavelength region and the green wavelength region, the infrared light on the longer wavelength side than the red wavelength region and on the shorter wavelength region side than the specific wavelength (900 nm) is cut and the specific wavelength is cut. The 2nd optical filter which permeate | transmits the infrared light longer than this is comprised.

  Among the plurality of pixels 20, provided in front of one or more pixels 20 that are not provided with the first optical filter and the second optical filter, transmit visible light in the green wavelength region and transmit in the blue wavelength region and the red wavelength region. The third optical filter is configured only by the G filter 22 that cuts visible light and transmits infrared light longer than the red wavelength region.

  In this embodiment, the first optical filter is configured by overlapping the B filter 23 and the infrared light cut filter 27, and the second optical filter is configured by overlapping the R filter 21 and the infrared light cut filter 27. However, the first optical filter transmits the visible light in the blue wavelength region and is specified on the longer wavelength side than the red wavelength region among the visible light and the infrared wavelength region in the green wavelength region and the red wavelength region. You may comprise only the B filter which cuts the infrared light of the short wavelength area side rather than a wavelength, and permeate | transmits the infrared light longer wavelength than a specific wavelength.

  Similarly, the second optical filter transmits visible light in the red wavelength region, and is longer than the red wavelength region and shorter than the specific wavelength among visible light and infrared wavelength regions in the blue wavelength region and the green wavelength region. You may comprise only the R filter which cuts the infrared light of the wavelength range side, and transmits the infrared light longer than a specific wavelength.

FIG. 11 is a graph of sensitivity characteristics showing the relationship between sensitivity and wavelength of a conventional image sensor.
In the conventional image sensor, as shown in FIG. 11, the peak of the pixel sensitivity Q6 for blue is near the wavelength 450 nm, the peak of the pixel sensitivity Q7 for green is near the wavelength 550 nm, and the pixel sensitivity Q8 for red This peak is in the vicinity of a wavelength of 620 nm.
Even in the conventional device, the sensitivity Q6 of the pixel corresponding to blue in the infrared region, the sensitivity Q7 of the pixel corresponding to green in the infrared region, and the sensitivity Q8 of the pixel corresponding to red in the infrared region are visible. Although it is lower than the sensitivity of the area, at night, the imaging target can be illuminated with invisible infrared light and displayed on the monitor so that the imaging target can be recognized.

In a normal vehicle-mounted camera not provided with an infrared illumination light source, when infrared light and visible light are mixed and sensed by the image sensor 6, the color tone is deteriorated when a color image is reproduced. Therefore, conventionally, an infrared light cut filter for cutting infrared light is provided in front of the image sensor, or the signal processing circuit unit 7 performs a process of removing the infrared signal component included in the video signal.
On the other hand, in the case of an in-vehicle camera with an infrared illumination light source, if an infrared light cut filter is provided in front of the image sensor, it is meaningless to perform infrared illumination. Usually it is not provided before. As a result, in the case of daytime shooting, since light including infrared light is received by the image sensor 6, it is inevitable that the color reproducibility deteriorates.

  Therefore, as disclosed in Japanese Patent Application Laid-Open No. 2007-212225, the light in the wavelength range of 700 nm to 850 nm is attenuated, and the pixel sensor (imaging device) of the short wavelength 850 nm side in the infrared region is attenuated. It is conceivable to improve color reproducibility by providing an optical filter in front of the pixel sensor that transmits light in all wavelength regions on the long wavelength side until the sensitivity becomes almost zero.

If an optical filter having such characteristics is used, when the wavelength of infrared light is a long wavelength of 850 nm or more, infrared light having a wavelength of 850 nm or more passes through the optical filter. However, the imaging object can be imaged without any problem.
However, with regard to color reproducibility during daytime photography, there is still a problem with color reproducibility, and particularly with regard to outdoor plant leaves, there is still a problem that hue is still poor during daytime photography.

  FIG. 12 shows an intensity distribution characteristic Q9 of sunlight reflected by a general plant leaf outdoors, and the reflection intensity of sunlight reflected by a plant leaf is a green wavelength from a wavelength of 500 nm to 600 nm corresponding to green. There are peaks in the region and the infrared wavelength region from 700 nm to 900 nm. In particular, since the reflection intensity of the infrared light reflected by the leaves of the plant is larger than the reflection intensity of the green light, the video signal output from the image sensor 6 when the reflected light from the leaves of the plant enters the image sensor 6. Therefore, there is a problem that it is difficult to determine at a glance what the driver is displaying because the leaf color that should be green is white and is displayed on the monitor.

  In this embodiment, the R filter 21, the G filter 22, and the B filter 23 have the transmittance characteristics shown in FIG. 9, and the infrared light cut filter 27 has the transmittance characteristics shown in FIG. Regarding the pixel (see FIGS. 7 and 8) 20 provided with the B filter 23, in terms of infrared light, the intensity of light reflected from the leaves of the plant is high in the infrared wavelength region of 700 nm to 900 nm. The infrared light is cut and the infrared light in the infrared wavelength region longer than 900 nm passes through the infrared light cut filter 27 and the R filter 21 (or B filter 23) and reaches the pixel 20. To do.

  On the other hand, regarding the pixel provided with the G filter 22, in terms of infrared light, the infrared light cut filter 27 having the transmittance characteristics shown in FIG. 10 is not provided, so the G filter 22 is provided. Infrared light having a wavelength of 700 nm or more reaches the pixel that passes through the G filter 22.

  That is, red light and infrared light having a wavelength of 900 nm or more reach the pixel 20 provided with the R filter 21 and the infrared light cut filter 27, and the B filter 23 and the infrared light cut filter 27 are provided. Blue light and infrared light having a wavelength of 900 nm or more reach the pixel 20 provided, and green light and infrared light having a wavelength of 700 nm or more reach the pixel 20 provided with the G filter 22. .

As described above, the wavelength component of the infrared light reflected from the leaves of the plant is in the infrared wavelength region from the wavelength of 700 nm to 900 nm. Therefore, the sensitivity characteristic of the image sensor 6 according to this embodiment is as shown in FIG. It will be as shown in
That is, among the light reflected from the leaves of the plant, the pixel 20 having sensitivity with respect to infrared light in the wavelength region of 700 nm to 900 nm is the pixel 20 provided with the G filter 22. The sensitivity Q10 of the pixel 20 is as shown by the broken line in FIG.

On the other hand, the sensitivity Q11 of the pixel 20 provided with the R filter 21 and the infrared light cut filter 27 is as shown by the alternate long and short dash line shown in FIG. The sensitivity Q12 of the provided image element 20 is as shown by a solid line in FIG.
The pixel 20 provided with the R filter 21, the pixel 20 provided with the G filter 22, and the pixel 20 provided with the B filter 23 are all for infrared light in a wavelength region having a specific wavelength of 900 nm or more. Therefore, when imaging an object that reflects infrared light in the wavelength region of 900 nm or more, the color signal output from each pixel 20 has the same magnitude, so the signal processing circuit unit 7 When processed and displayed on the monitor 2, it is displayed as a gray object.

  On the other hand, when an image of an object that reflects a green wavelength region from a wavelength of 500 nm to 600 nm and an infrared wavelength region from 700 nm to 900 nm is imaged, an output of a color signal from the pixel 20 provided with the G filter 22 is performed. Is much larger than the color signal output from the pixel 20 provided with the R filter 21 and the pixel 20 provided with the B filter 23, and is processed by the signal processing circuit unit 7 and displayed on the monitor 2. Displayed as a green object. Accordingly, when a plant leaf is photographed in the daytime, it is displayed on the monitor 2 as a green object.

  In this embodiment, not only the leaves of plants but also all objects reflecting sunlight in the infrared wavelength region from 700 nm to 900 nm are displayed in green on the monitor 2. As long as shooting is performed, an object that reflects sunlight in a wavelength region of 700 nm to 900 nm is almost only a plant, so that an image without a feeling of strangeness can be displayed on the monitor 2.

  As described above, when infrared light in the wavelength region from 700 nm to 900 nm is incident on the image sensor 1, the monitor 2 displays a green color. Therefore, the emission characteristics in the wavelength region from 700 nm to 900 nm can be obtained during night driving. When an object is photographed using the infrared light emitting diode 17 having the color filter, only the color signal of the pixel 20 provided with the G filter 22 is output, so that it is not only displayed as a green object on the monitor 2 but also the entire screen. Becomes green, and a sense of incongruity is caused when shooting at night.

  In this embodiment, the light emission characteristic Q1 of the infrared light emitting diode 17 is illuminated with infrared light in the wavelength region of 900 nm to 1000 nm, and all the pixels 20 have infrared light in the wavelength region of 900 nm or more. The object displayed on the monitor 2 is illuminated with the infrared light emitting diode 17 having the light emission characteristic Q1 according to this embodiment when traveling at night. Is displayed in black and white, and the captured image is displayed on the monitor 2 without a sense of incongruity even during night driving. This is the reason why the infrared light emitting diode 17 having the light emission characteristic Q1 in the wavelength region of 900 nm to 1000 nm is used for night illumination.

  That is, in this embodiment, the specific wavelength is set in the vicinity of the upper limit wavelength limit of the wavelength region of the reflection intensity distribution characteristic of the plant, so that it is possible to improve the reproducibility of the plant leaf color during daytime photography. Even when the infrared light is illuminated at night, the infrared light emitting diode 17 having a light emission characteristic in a wavelength region of a specific wavelength or more is used, so that a photographed image can be displayed on the monitor 2 without a sense of incongruity.

FIG. 14 is an explanatory diagram showing an example in which the front wheel 29 of the automobile 28 is photographed using the in-vehicle camera 1 according to this embodiment. In FIG. 14, reference numeral 30 denotes an imaging target area. In FIG. 14, the in-vehicle camera 1 is provided in the outside mirror device 14 on the side opposite to the driver's seat.
The signal processing circuit unit 7 cuts out an image from the imaging target region 30 and outputs an image only near the front wheel 29 toward the monitor 2. Thereby, an image near the front wheels is displayed on the monitor 2.

  When traveling at night, the infrared light emitting diode 17 emits light, and the infrared light is collected by the illumination lens 5 to illuminate the imaging target region 30. Since the infrared light emitted from the infrared light emitting diode 17 is condensed using the illumination lens 5 and only the imaging target region 30 is illuminated, the infrared light emitted from the infrared light emitting diode 17 is efficiently captured. Irradiation can be performed toward the region 30, and power can be saved.

6 ... Image sensor 20 ... Pixel 21 ... Red filter 22 ... Green filter 23 ... Blue filter 27 ... Infrared light cut filter

JP 2007-221225 A JP-A-10-108206 JP 2002-320139 A Japanese Patent No. 4286123

Claims (7)

A plurality of pixels having sensitivity to light in a wavelength region from the visible region to the infrared region;
The red wavelength region is provided in front of at least one of the plurality of pixels and transmits visible light in a blue wavelength region, and the red wavelength region in visible light and infrared wavelength regions in a green wavelength region and a red wavelength region. A first optical filter that cuts infrared light on a longer wavelength side and shorter wavelength region side than a specific wavelength and transmits infrared light on a longer wavelength side than the specific wavelength;
Visible light in the red wavelength region and visible light in the blue wavelength region and the green wavelength region are provided in front of one or more pixels in which the first optical filter is not provided among the plurality of pixels. In the infrared wavelength region, infrared light on the longer wavelength side than the red wavelength region and on the shorter wavelength region side than the specific wavelength is cut, and infrared light on the longer wavelength side than the specific wavelength is transmitted. A second optical filter,
Among the plurality of pixels, the first optical filter and the second optical filter that are not provided are provided in front of one or more pixels to transmit visible light in the green wavelength region and the blue wavelength region, A third optical filter that cuts visible light in a red wavelength region and transmits infrared light on a longer wavelength side than the red wavelength region;
An image sensor comprising: The first optical filter transmits blue light in the blue wavelength region, cuts visible light in the green wavelength region and the red wavelength region, and transmits infrared light on a longer wavelength side than the red wavelength region. A filter and an infrared light cut filter that cuts light on a shorter wavelength side than the specific wavelength and transmits infrared light on a longer wavelength side than the specific wavelength are overlapped,
The second optical filter transmits red light in the red wavelength region, cuts visible light in the blue wavelength region and the green wavelength region, and transmits infrared light on a longer wavelength side than the red wavelength region. A filter and an infrared light cut filter that cuts light on a shorter wavelength side than the specific wavelength and transmits infrared light on a longer wavelength side than the specific wavelength are overlapped,
The third optical filter transmits green light in the green wavelength region, cuts visible light in the blue wavelength region and the red wavelength region, and transmits infrared light on a longer wavelength side than the red wavelength region. The image sensor according to claim 1, wherein the image sensor is configured by a filter.   The image sensor according to claim 1, wherein the specific wavelength is set in the vicinity of a limit of an upper limit wavelength of a wavelength region of a reflection characteristic of a plant leaf.   The image sensor according to claim 1, wherein the specific wavelength is a wavelength near 900 nm.   The image sensor according to any one of claims 1 to 4, a signal processing circuit unit that processes a video signal output from the image sensor, an illumination light source circuit unit that illuminates an imaging target region, and A control circuit unit that controls the image sensor, the signal processing circuit unit, and the illumination light source circuit unit, and the illumination light source circuit unit includes a light emission source having a light emission characteristic on a longer wavelength side than the specific wavelength. An imaging apparatus characterized by that.   The imaging device according to claim 5, wherein the light emitting source is an infrared light emitting diode.   An in-vehicle monitoring device comprising: the imaging device according to claim 5 or 6 provided in a vehicle; a monitor provided in the vehicle; and an external control device provided in the vehicle to control the imaging device.