CROSS REFERENCE

This application is the U.S. National Phase under 35 U.S.C. § 371 of International Application No. PCT/JP2016/066612 filed on Jun. 3, 2016, the entire contents of each are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to an imaging apparatus and an imaging system.

BACKGROUND ART

A combination of image recognition technology and biometric authentication has been recently used to advance development of: surveillance cameras for detecting criminals, shoplifters, and terrorists, etc. by face authentication; and in-vehicle cameras utilized for automatic driving of automobiles.

For example, known has been a system in which a surveillance camera detects a distance by using a stereo camera and detects intrusion of suspicious individuals (see Patent Document 1). Patent Document 1 discloses a “distance-measurement image recognition apparatus using a stereo image(s)” as a method of measuring a shape and distance of an object. Known has been a technique called a stereo method for obtaining a distance(s) from a stereo image(s). In this stereo method, first, two right and left images called stereo images are inputted, and corresponding points of the right and left images (where a target object at a certain position of the left image is projected in the right image) are obtained by calculating a feature amount of the images. Details of how to obtain the corresponding points are described as an “image matching method” in, for example, Patent Document 2. Obtaining the corresponding points of the right and left images then makes it possible to calculate a distance to an object surface by the triangulation's principle, so that the distance to the object and the shape of the object surface can be known.

Patent Document 1 also proposes a moving-object recognition apparatus that can detect a moving object(s) with high accuracy and high speed and measure its shape and distance by using a known correspondence relationship with a stereo image(s).

Surveillance cameras and automatic driving cameras are required so as to photograph regardless of location and time such as outdoor and indoor locations, and day and night. However, no sufficient illumination may be often obtained depending on such a situation in photographing. In this case, it is conceivable to take an infrared photography by using infrared illumination which human beings cannot see. It is conceivable to take an infrared photography by using infrared light as illumination for illuminating a distant place in consideration of an influence of headlight on an oncoming vehicle(s) at night also in the automatic driving camera. In any case, it is conceivable to take a visible-light photography, without illumination, in the daytime which there is a high possibility of making an amount of visible light sufficient, and to take the infrared photography by using the infrared illumination, which it is difficult for human eyes to catch, in needing night illumination.

Considering such situations, it is preferable that each of the surveillance camera and the automatic driving camera can simultaneously photograph with the visible light and infrared light.

An imaging apparatus such as a surveillance camera continuously photographing day and night detects infrared light and photographs at nighttime. A photodiode (light receiving element) serving as a light receiving portion of an imaging sensor such as a CCD sensor or CMOS sensor can receive light up to a near infrared wavelength band of about 1300 nm, so that the imaging apparatus using those imaging sensors makes it possible in principle to photograph up to an infrared band.

Incidentally, a wavelength band of light with high human's visibility is 400 nm to 700 nm, so that when the imaging sensor detects near-infrared light, the human eyes appear reddish on an image(s) detected by the sensor. This makes it desirable to provide, in front of the imaging sensor, an infrared cut filter for blocking light in the infrared band and to remove light having a wavelength of 700 nm or more in order to match sensitivity of the imaging sensor with the visibility of the human beings in photographing in the daytime or at an indoor bright place(s). Meanwhile, providing no infrared cut filter is required in photographing at night or in a dark place.

Conventionally known as the above-mentioned imaging apparatus have been: an imaging apparatus that an infrared cut filter is manually attached to or detached from; or an imaging apparatus that an infrared cut filter is automatically inserted into and removed from. Furthermore, disclosed is an imaging apparatus not requiring the insertion and removal of the above-described infrared cut filter. For example, proposed is an optical filter having; a transmission characteristic in a visible light band; a cutoff characteristic in a first wavelength band adjacent to a long wavelength side of the visible light band; and a transmission characteristic in a second wavelength band which is a part of the first wavelength band (see Patent Document 3). This filter makes it possible to transmit light in both of the visible light band and a second wavelength band which is away from the visible light band on a long wavelength side, i.e., an infrared side of the visible light band.

Hereinafter, called a DBPF (double band pass filter) will be the optical filter that transmits, as mentioned above, light in the visible light band and light in the second wavelength band on the infrared side and blocks light in the other wavelength band.

Additionally, recently advanced as biometrics authentication has development of various authentication technologies such as fingerprints, faces, irises, veins, signatures, voiceprints, and walking. However, recited as biometrics authentication used with image recognition technologies about the images captured by the above-described surveillance camera and automatic driving camera are face authentication and iris authentication.

RELATED ART DOCUMENTS

Patent Documents

Patent Document 1: Japanese Patent Application laid-open No. H3-81878

Patent Document 2: Japanese Patent Application laid-open No. S62-107386

Patent Document 3: Japanese Patent No. 5009395

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

The DBPF of Patent Document 3 does not block, all the time, the light in the second wavelength band (a comparatively narrow wavelength band included in the infrared wavelength band) included in the infrared (near infrared) wavelength band, and causes the light to be transmitted. That is, unlike a case of using the infrared cut filter that cuts the long wavelength side of the visible light band, the photography in the visible light band is subjected to no little influence of infrared light transmitting the second wavelength band.

For the photography in the visible light band, a color filter is used in the imaging sensor that takes a color photography. Color filters, which correspond to respective pixels of the imaging sensor and in which respective color regions (filter portions) of red, green, and blue are arranged in a predetermined pattern, basically have a peak of transmittance of light in each color wavelength band and block transmission of light in the other color wavelength bands.

However, the long wavelength side of the visible light band has a different light transmittance depending on each color region and wavelength, but basically leads to transmitting of light. Therefore, if transmitted in the second wavelength band on the infrared side like the above-described DBPF, the infrared light passes through the color filter and reaches the photodiode (light receiving element) of the imaging sensor, thereby bringing an increase in an amount of electrons generated by the photoelectric effect due to the photodiode.

Further, in performing both of color photography with visible light and photography with infrared light illumination, for example, the color filter in which the respective color regions of red, green, and blue are arranged in the predetermined pattern(s) is provided with an infrared light region (infrared region) that has a peak of the light transmittance in the above-mentioned second wavelength band. That is, an arrangement (pattern) of the color filters is composed of four regions of red R, green G, blue B, and infrared IR. In this case, the infrared light region blocks the light in the visible light band and mainly transmits the light in the second wavelength band. Therefore, it is conceivable that an infrared light component(s) is removed from an image signal of each color of red, green, and blue by using an image signal of infrared light outputted from the imaging sensor which receives light passing through the infrared light region of the color filter. However, even such a signal processing has made it difficult to reproduce almost the same color as that in having color-photographed through use of the infrared cut filter. When right and left signals are made stereo to calculate a distance, some deviation between right and left signal levels has brought a factor of generating an error(s) in parallax calculation.

Furthermore, when face authentication is used by utilizing a photographed image(s) of a camera, there are roughly two types of face authentication; a type in which a user adjusts a user's face on a predetermined camera in an entry/exit management system of an office or building, a boarding procedure at an airport, immigration/registration management, or the like; and a type of authenticating a unspecified large number of users that the user has unknowingly photographed by a plurality of cameras at locations such as public facilities, airports, or transportation facilities for the purpose of pursuit of criminals, prevention of terror, and early detection of suspicious individuals, etc. The former type can recognize the face authentication with high precision even by recent technologies since photographing conditions are limited. Meanwhile, the latter type greatly influences a recognition rate since photographing conditions such as illumination condition, face direction, and angles greatly vary due to an environmental change(s).

In order to perform suspicious-individual detection by using surveillance cameras, use of both visible light and infrared light makes it possible to continuously photograph for 24 hours without depending on a photographing location(s) and a photographing time. Further, if the photographed image can be made as clearly as possible with less noise and higher resolution, the ability to early detect a suspicious individual(s) and to analyze a situation(s) at a time of crime is expected to be significantly improved.

Additionally, when the photography with infrared light and the photography with visible light as described above are used in combination, even the automatic driving camera that has a configuration of measuring a distance through a stereo method by using the two cameras obtains a clear image(s) with less noise, thereby being capable of achieving improvement of accuracy of the image recognition.

From the above, it is desirable that: simultaneous photography of both of an infrared image and a visible image is possible; a level of image quality such as noise, resolution, and color reproducibility is equal to or more than that of a visible image including no normal infrared image; and further stereo photography is possible with two camera configurations.

The present invention provides a technique capable of: photographing both of a visible image(s) and an infrared image(s) and capturing a high quality image(s) by improving color reproducibility at a time of photographing with visible light.

Means for Solving the Problems

An imaging apparatus or imaging system according to the present invention includes: an imaging element; a filter configured to have at least a characteristic of transmitting a visible light wavelength range and an infrared light wavelength range and to filter a signal from the imaging element based on the characteristic; a signal processor configured to process the signal filtered by the filter to output a visible light signal and an infrared light signal; a moving-object region extractor configured to generate, from the infrared signal outputted from the signal processor, information on a moving object in an image photographed by the imaging element; and a signal output controller configured to transmit, outside, a first data containing at least one of the visible and infrared light signals outputted from the signal processor, and a second data based on information on the moving object generated by the moving-object region extractor.

Further, an imaging apparatus or imaging system according to the present invention includes: two imaging elements; two filters configured to have at least a characteristic of transmitting a visible light wavelength region and an infrared wavelength region and to filter signals from the imaging elements based on the characteristic; two signal processors configured to process the signals filtered by the filters and to output a visible light signal and an infrared light signal; a distance calculator configured to use two visible image signals and/or two infrared image signals outputted from the signal processors to calculate a distance to a to-be-photographed subject that has been photographed with a visible image based on the visible image signals and/or an infrared image based on the infrared image signals; a moving-object region extractor configured to generate, from the infrared signals outputted from the signal processors, information on a moving object in an image photographed by the imaging elements; and a signal output controller configured to transmit, outside, a first data that contains at least one of the visible or infrared light signals outputted from the signal processors, a second data that is based on information on the moving object generated by the moving-object region extractor, and a third data that is based on a distance image generated by the distance calculator.

Effects of the Invention

The present invention makes it possible to obtain an image(s) with high quality. More specifically, for example, one aspect of the present invention makes it possible to simultaneously photograph both of high-quality infrared and visible images with a camera that is configured by one imaging sensor and one optical film, and so to improve visibility even under nighttime or an environmental change such as insufficient lighting. Further, another aspect of the present invention makes it possible to measure more accurately a distance of the object with both of the infrared and visible images, and to provide its information to an exterior system together with the visible or infrared image. Additionally, yet another aspect of the present invention makes it possible to extract a moving object in an image with higher speed by using not the visible image but the infrared image, and to provide its information to an exterior system together with the visible or infrared image.

