JP2016103786A - Imaging system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging system that can simultaneously perform imaging of a visible image and imaging of an infrared image to photograph a visible image and infrared image of a person within the same imaging range, recognize the face of the person in the visible image, and measure vital signs, including pulse and body temperature from the infrared image of a skin area of the face, and is compact and can be manufactured at a low cost.SOLUTION: An imaging sensor 115 includes: a color filter 113; and a DBPF 111 that has permeation characteristics in a visible light band, has cut-off characteristics in a first wavelength band adjacent to a long-wavelength side of the visible light band, and has permeation characteristics in a second wavelength band that is a part in the first wavelength band. A signal processing part 116 subtracts an infrared signal to be output from infrared pixels from signals in respective colors to be output from pixels in respective colors of the visible light in the imaging sensor 115. The imaging sensor 115 recognizes the face in the visible image and detects a pulse rate and temperature from the skin of the face in the infrared image.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an imaging system that acquires information by simultaneously performing imaging with visible light and imaging with infrared light in the same imaging range.

  In recent years, image recognition technology has advanced. For example, a digital camera can recognize a human face by face recognition and focus on the face. Furthermore, it is also possible to recognize and specify the face of a person whose face image data is registered in advance from the image data of the surveillance camera. However, in the case of face recognition, the face of a photograph such as a poster may be erroneously recognized as a human face. Then, the proposal which recognizes a face from the image recognition by visible light and the heat detection (body temperature detection) by infrared light is made | formed (for example, refer patent document 1).

  In this case, photographing with visible light and photographing with infrared light are performed by one camera, and the temperature of the face position specified by face recognition using visible light image data is determined from the infrared light image data. Since it recognizes and recognizes a face and recognizes a region where the temperature is high as a face, a face photo of a poster whose temperature is lower than the body temperature is not erroneously recognized as a human face.

  In Patent Document 1, a plurality of structures are proposed in which photographing with visible light and infrared light is performed simultaneously or switched. Here, an imaging device such as a digital camera has a light receiving sensitivity for light from visible light to near infrared, and an infrared light cut filter that cuts infrared light and transmits visible light, or visible light. By separately using a visible light cut filter that cuts and transmits infrared light, it is possible to capture visible light and infrared light. In this case, as an imaging system including a lens and an image sensor, an imaging system including an infrared light cut filter and an imaging system including a visible light cut filter are provided in one camera, or one imaging system. Therefore, it is necessary to provide an infrared light cut filter and a visible light cut filter in a switchable manner.

  In addition, it is known that infrared light can detect not only the body temperature but also the pulse rate (heart rate). For example, in capillaries on the surface layer of the skin, the capillaries are expanded and contracted by the pulse corresponding to the heartbeat. When the capillaries are inflated, the amount of blood in the capillaries is large, and the blood hemoglobin is also increased accordingly. Conversely, when the capillaries are contracting, the amount of blood in the capillaries is small, and the blood hemoglobin is also correspondingly reduced. Therefore, the amount of hemoglobin on the surface layer of the skin increases or decreases in synchronization with the pulse.

  Hemoglobin is known to absorb near infrared light. Therefore, when the amount of hemoglobin on the surface layer of the skin decreases, the amount of reflected near-infrared light increases, and when the amount of hemoglobin increases, the amount of reflected near-infrared light decreases. Therefore, the amount of reflected infrared light that increases and decreases in synchronization with the leaf foil is detected by the LED as a light emitting element that outputs near infrared light and the infrared light sensor as a light receiving element that detects near infrared light. By doing so, the pulse rate can be measured. Since the amount of reflected infrared light changes in synchronization with the pulse, it is possible to detect the pulse rate substantially in real time by taking and analyzing an infrared image of a human skin, for example, a face as a moving image. .

  In addition, with a monitoring camera or the like, visible light and infrared light are simultaneously photographed. From the visible light, for example, the face area of a person to be observed in a hospital or facility is detected, and the corresponding infrared light face area is detected. In addition to detecting body temperature, it has been proposed to detect a pulse from a face region of visible light (see, for example, Patent Document 2). Note that the color of the face changes slightly depending on the pulse from the change in the amount of hemoglobin that is red by absorbing light in the green wavelength range due to the expansion and contraction of the above-mentioned capillaries, so visible light It is possible to detect the pulse rate from the moving image data.

  In Patent Document 2, a half mirror is used to divide input light into two parts, an image sensor is disposed on one of the two light sides via an infrared cut filter, and a visible light cut filter (band) is provided on the other light side. By arranging an image sensor via a pass filter, a moving image of visible light and a moving image of infrared light are simultaneously photographed. Moreover, in patent document 2, as a color filter provided in the image pick-up element for color imaging | photography, each area | region of visible light of red (R), green (G), and blue (B), and the infrared which lets infrared light pass. There has been proposed a method of photographing a color image and an infrared image with one image sensor by providing an (IR) region.

Japanese Patent No. 4702441 JP 2014-36801 A

  By the way, in the case of an imaging device that captures both a visible light image and an infrared light image at the same time, an imaging device using an infrared cut filter for visible light and a visible light cut filter for infrared light. In the case of using both of the image pickup device using, it is necessary to use at least two image pickup devices, which makes it difficult to reduce the size and to reduce the cost.

  In addition, when the image input from the optical system is separated in two directions by the half mirror and the separated images are picked up by separate image pickup devices, it is difficult to reduce the size. In addition, when two image sensors are used, the two moving image data captured by each image sensor have a slight positional shift, so when image processing is performed using the same coordinate system with two image data, It is necessary to correct the misalignment.

  In addition, in the case of an imaging device that switches between an infrared cut filter and a visible light cut filter, the structure for switching the filter is costly, and it is difficult to capture a visible image and an infrared image at the same time. In the case of a structure that repeatedly moves the filter, the number of frames that are captured per time is limited.

  On the other hand, in the method in which the IR region is provided in the color filter provided in the imaging element in addition to the RGB regions of visible light as described above, the size can be reduced and the increase in cost can be suppressed. However, an infrared cut filter is used in a digital camera including an image pickup device using a color filter composed of RGB regions without a general IR region. This is because in the color filter, each color region of RGB has a transmittance peak in the wavelength range of each color and has a blocking characteristic in the wavelength range of other colors, but is closer to the longer wavelength side than visible light. It is based on having transmission characteristics in the infrared.

  That is, a general color filter requires an infrared cut filter in order to cut infrared light that passes through each color region of the color filter. Therefore, for example, even if an IR region that blocks visible light and transmits near-infrared light is provided in the color filter, if the infrared cut filter is not used, pixels of the image sensor corresponding to each region of RGB are used. Infrared light will be input in addition to light in the wavelength range corresponding to each of RGB, and the amount of charge output from the light receiving element of each pixel of the image sensor will increase accordingly, and the infrared cut filter will be It is difficult to obtain a natural color image as compared with the case of using it. Further, if an infrared cut filter is used, there is a problem that an infrared image cannot be captured even if an IR region is provided in the color filter.

  Therefore, by providing an IR region that blocks visible light and transmits near-infrared light in the color filter, for example, a visible light cut filter is not necessary, but an infrared cut filter is required and an infrared image is also required. When photographing the image, it is necessary to remove the infrared cut filter. That is, a configuration for switching the presence or absence of an infrared cut filter is required, and it is difficult to capture a visible image and an infrared image at the same time.

  The present invention has been made in view of the above-described circumstances, and simultaneously captures a visible image and an infrared image, and recognizes a person's face within the same imaging range in the visible and infrared as a visible image. It is another object of the present invention to provide an imaging system that can measure vital signs such as pulse rate and body temperature from an infrared image of the skin area of the face, and that is compact and can be manufactured at low cost.

In order to solve the above problems, an imaging system of the present invention provides:
An imaging sensor comprising an image sensor main body in which a light receiving element is arranged for each pixel, and a color filter in which a plurality of visible light regions and an infrared light region are arranged in each pixel of the image sensor main body in a predetermined arrangement When,
An optical system having a lens for connecting an image on the imaging sensor;
A transmission characteristic in the visible light band, a cutoff characteristic in the first wavelength band adjacent to the long wavelength side of the visible light band, and a second wavelength band that is a part of the first wavelength band; An optical filter having transmission characteristics;
Based on the signal output from the imaging sensor, a process of subtracting the infrared light component signal from the visible light component signal is performed to obtain a visible image signal and an infrared image signal in the same imaging range. Signal processing means capable of outputting simultaneously;
Visible image processing means for specifying a region of a human face in the image of the visible image signal;
And infrared image processing means for measuring at least a part of a vital sign from an image of the face area of the person specified by the visible image processing means in the image of the infrared image signal.

  According to such a configuration, an imaging sensor including a color filter having a visible light region and an infrared light region, and a transmission characteristic in a second wavelength band that is a near infrared band far from the visible light band and the visible light band. The visible image signal output without using the infrared cut filter is obtained by subtracting the infrared light component signal from the signal of each color component by the signal processing means. It will be in the state where an ingredient is not contained. Note that the infrared light that passes through the second wavelength band of the optical filter passes through the IR region of the color filter. Hereinafter, an optical filter having light transmission characteristics in the visible light band and the infrared second wavelength band may be referred to as a DBPF (double band pass filter).

  Further, the infrared light component included in the visible light component of each color that has passed through each color region of visible light is only the infrared light that has passed through the second wavelength band of DBPF. The infrared light component that has passed through the IR region of the color filter is a component of infrared light that has passed through the second wavelength band of the optical filter. Therefore, the wavelength range of the infrared component included in the visible light is limited by DBPF so that the wavelength range of the infrared light that can pass through the IR region that blocks the visible light of the color filter substantially includes the second wavelength band. If so, it becomes possible to remove the infrared component whose wavelength range is limited as described above from the visible light component of each color, and more accurately remove the infrared light component contained in the visible light component of each color. It becomes possible to do.

  As a result, even if there is no infrared cut filter, it is possible to obtain a natural visible image close to the case where a conventional infrared cut filter is used. Infrared image signals can be output at the same time, and vital signs such as body temperature and pulse can be read from the skin area of the face of the infrared image based on face recognition using a visible image.

  In this case, simultaneous imaging of visible image and infrared image can be performed with one image sensor, and pulse rate and body temperature can be measured with infrared image based on human face area specified by visible image In the imaging system described above, the number of imaging elements can be reduced to one, the filter switching device is not required, the imaging system can be reduced in size, and the cost of the imaging system can be reduced.

  In addition, since the image pickup is performed using a color filter including the IR region with one image sensor, there is no shift in the shooting range between the visible image and the infrared image. Each pixel of the outer image corresponds to each other. Therefore, it is not necessary to correct the positional deviation as in the case of using two image sensors.

  The visible light band is a wavelength band of about 400 nm to 700 nm, the first wavelength band is a wavelength band of about 700 nm or more as the near-infrared wavelength band, and the second wavelength band is, for example, 800 nm to A wavelength band of about 1100 nm or a wavelength band included in this wavelength band and narrower than this wavelength band.

In the configuration of the present invention, the optical system includes, in order from the object side to the image side, a first lens having negative power, a second lens having negative power, a third lens having positive power, and A fourth lens with positive power,
The fourth lens is a cemented lens including an object side lens having a negative power and an image side lens having a positive power, and a resin adhesive layer that bonds the object side lens and the image side lens. Prepared,
The image side lens surface of the object side lens and the object side lens surface of the image side lens have different aspherical shapes, respectively.
The thickness of the resin adhesive layer on the optical axis is D, and the image side lens of the object side lens at the height H at the effective diameter of the image side lens surface of the object side lens in the direction orthogonal to the optical axis. When the sag amount of the surface is Sg1H and the sag amount of the object side lens surface of the image side lens at the height H is Sg2H, it is preferable that the following conditional expressions (1) and (2) are satisfied.
20 μm ≦ D (1)
Sg1H ≦ Sg2H (2)

  According to such a configuration, in the optical system (imaging lens) of the present invention, the image side lens surface of the object side lens and the object side of the image side lens which are the cemented surfaces of the two lenses constituting the cemented lens. The lens surfaces are different aspherical shapes. As a result, it becomes easy to correct various aberrations such as chromatic aberration using the cemented lens, so that the resolution of the imaging lens can be increased. Further, since the conditional expression (1) and the conditional expression (2) are satisfied, the resin adhesive layer between the image side lens surface of the object side lens and the object side lens surface of the image side lens, which are different aspherical shapes from each other , That is, the interval between the cemented surfaces of the two lenses constituting the cemented lens can be widened.

  Therefore, it is possible to prevent or suppress the bonding surfaces from being brought into contact with each other during the bonding operation of bonding the two lenses and causing damage to each bonding surface. Moreover, since the space | interval of a joining surface is wide, it can prevent that a resin adhesive agent wraps around between joining surfaces, and a bubble remains between two lenses. Therefore, it becomes easy to manufacture the cemented lens. Furthermore, the imaging lens can be designed with an interval between the image side lens surface of the object side lens constituting the cemented lens and the object side lens surface of the image side lens on the optical axis being set to 20 μm or more in advance. It is possible to design in consideration of the shift of the field curvature to the plus side, and the design can suppress the shift of the field curvature to the plus side. The sag amount is the lens surface from the reference surface at the height H at the effective diameter in the direction orthogonal to the optical axis when a plane that includes the intersection of the lens surface and the optical axis and is orthogonal to the optical axis is used as the reference surface. Is the distance in the optical axis direction. In such an optical system of the present invention, it is possible to prevent or suppress the occurrence of a focus shift between photographing using visible light and photographing using near infrared rays. Therefore, when taking a visible image and an infrared image at the same time as described above, even if the same optical system is used at the same time, it is possible to prevent or suppress the occurrence of a focus shift in either the visible image or the infrared image. it can.

  Therefore, for example, it can be suitably used for an optical system of an imaging system that simultaneously performs imaging using near-infrared light included in a band of 800 nm to 1100 nm and imaging using visible light. That is, in a general optical system, the problem of chromatic aberration is solved within the visible light band, but the visible light band of 400 nm to 700 nm and the infrared band light included in the range of 800 nm to 1100 nm. When shooting simultaneously, the difference in refractive index is larger than in the visible light band alone, and the focal point is shifted between the wavelength in the center of the visible light band and the wavelength in the infrared band. When focusing, the infrared image will not be focused. However, by using this optical system, when focusing on a visible image, it is possible to prevent the focus of the infrared image from deviating greatly, and it is easy to simultaneously capture a visible image and an infrared image with one optical system. It can be carried out.

  Further, in the configuration of the present invention, the optical system has a position where the infrared light passing through the second wavelength band of the optical filter and the infrared light region of the color filter is focused. It is preferable to provide a hologram that matches the focal position where the light beam in the visible light band is focused.

  According to such a configuration, the optical system refracts the infrared light passing through the second wavelength band of the optical filter and the infrared light region of the color filter by the hologram, and the infrared light is focused. Since the connecting position is made coincident with the focal position of the light beam in the visible light region, it is possible to suppress the occurrence of a problem that one of the visible image and the infrared image is out of focus in the above-described conventional optical system. In this case, the optical filter having transmission characteristics in the visible light band and the near-infrared second wavelength band is preferably on the object side of the hologram, and is preferably disposed on the object side of the optical system. .

  The said structure of this invention WHEREIN: It is preferable that the said vital sign is a pulse and / or body temperature.

  According to such a configuration, when the imaging system of the present invention is used in a surveillance camera system, a person who seems to be in poor physical condition because the body temperature is high or the pulse rate is high in the imaging range of the surveillance camera. It becomes possible to specify. For example, in a surveillance camera at an airport or a port, it is possible to specify that a traveler from abroad is in poor health, and it is possible to specify a person suspected of having an infectious disease. Also, for example, a person who commits a criminal act may become nervous and the pulse rate may be abnormally high. For example, by identifying a person with a high pulse rate and asking a job question, etc. There is a possibility that can be prevented. Further, in a hospital or the like, it is possible to identify a person who is extremely unwell with a monitoring camera and perform a diagnosis, or to advance the order of the diagnosis. Various vital sign measurement methods using infrared light have been studied. For example, not only the pulse rate but also blood flow can be measured, and vital signs are not limited to the pulse rate and body temperature.

  In the configuration of the present invention, at least two of the signal processing unit, the visible image processing unit, and the infrared image processing unit are configured by an electronic circuit on one chip and are made into one chip. preferable.

  According to such a configuration, the signal processing means, the visible image processing means, the infrared image processing means, or two or more of them can be integrated into one chip, so that the number of parts of the actual imaging system can be increased. The cost can be reduced, the device configuration can be simplified, the assembly work can be facilitated, and the size can be reduced.

  According to the imaging system of the present invention, a visible image that does not include an infrared component and an infrared image can be obtained without using an infrared cut filter with a single imaging device. Therefore, it is possible to manufacture an imaging system that recognizes a person's face with a visible image and obtains a vital sign from an infrared image of the face-recognized region in a compact and low-cost manner.

1 is a schematic block diagram illustrating an imaging system according to a first embodiment of the present invention. It is a figure for demonstrating an imaging lens equally. It is a figure for demonstrating an imaging lens equally. It is a figure for demonstrating an imaging lens equally. It is a figure for demonstrating an imaging lens equally. It is a figure for demonstrating the arrangement pattern of the color filter which has an infrared region similarly. It is a graph which shows the transmittance | permeability spectrum of DBPF and a color filter of the said image sensor. It is a graph which shows the relationship between a pulse and the output level of an infrared signal similarly. It is the graph which isolate | separated the wave which shows a pulse rate from the wave of the output level of an infrared signal similarly. It is a figure for demonstrating the monitor display of a person with abnormality in a pulse and body temperature. 3 is a flowchart for explaining an image processing method. It is a figure for demonstrating the imaging lens of the 2nd Embodiment of this invention. It is a figure for demonstrating an imaging lens equally.

Embodiments of the present invention will be described below.
As shown in FIG. 1, the imaging system 100 according to the present embodiment measures vital signs such as body temperature and pulse rate (heart rate) of a person (subject) 101 within the imaging range, and abnormal vital signs are detected. A certain person 101 is detected.

  The camera 110 used in the imaging system 100 includes a DBPF 111 as an optical filter, an imaging lens 10 that is an imaging optical system, an imaging sensor 115 including a color filter 113 and a sensor body 114, and an output from the imaging sensor 115. Processing the output signal, image processing such as synchronization processing (interior processing), removal of IR components from each RGB component of visible light, gamma correction, white balance, RGB matrix correction, etc. And a signal processing unit (signal processing means) 116 applied to the image signal. A color visible image signal 121 and an infrared image signal 122 can be output from the signal processing unit 116.

  The imaging system 100 includes a visible image processing unit (visible image processing unit) that performs processing for recognizing the face of the person 101 within the imaging range based on the visible image signal 121 including RGB signals output from the camera 110 described above. ) 117, and based on the infrared image signal 122 and the position of the skin region of the person 101 within the imaging range (frame) specified by the visible image processing unit 117, the body temperature and pulse rate of the person 101 are calculated. When the body temperature and the pulse rate of the person 101 in the captured image are measured by the infrared image processing unit (infrared image processing unit) 118 to measure and the infrared image processing unit 118, the body temperature in the measurement data is measured. And whether or not there is an abnormality in either the pulse rate or the pulse rate, and identification image data for identifying an image of the person 101 with an abnormal body temperature or pulse rate is output to the visible image processing unit 117 An identification image based on identification image data that makes it possible to recognize the person 101 having an abnormality in body temperature or pulse rate from the visible image signal 121 based on the visible image signal 121 from the abnormality determination unit (abnormality determination unit) 119. And a monitor 120 for displaying the added image.

  In the imaging system 100, the signal processing unit 116, the visible image processing unit 117, the infrared image processing unit 118, and the abnormality determination unit 119 are configured by an electronic circuit (integrated circuit) such as a general-purpose microcomputer or a dedicated gate array. These are mounted on a single chip to form a single chip. It should be noted that even when the signal processing unit 116, the visible image processing unit 117, the infrared image processing unit 118, and the abnormality determination unit 119 are configured by both a general-purpose microcomputer and a dedicated gate array, it is preferable to use one chip. . Further, it is not necessary to make all of the signal processing unit 116, the visible image processing unit 117, the infrared image processing unit 118, and the abnormality determination unit 119 into one chip, but as many as possible in one or more of these two or more. It is preferable that One-chip configuration can reduce costs, reduce size, and facilitate assembly.

  The imaging lens 10 constitutes an optical system that connects an image on the imaging sensor 115 of the imaging system 100. In the present embodiment, in order to obtain a state in which both the visible image and the infrared image are substantially in focus even if the imaging of the visible image and the imaging of the infrared image are performed by the group of imaging lenses 10, the following is performed. The imaging lens 10 having the structure as described above is used.

  As shown in FIG. 2, the imaging lens 10 of this example includes, in order from the object side to the image side, a first lens 11 having a negative power, a second lens 12 having a negative power, and a positive power. It consists of a third lens 13 and a fourth lens 14 with positive power. A diaphragm 15 is disposed between the third lens 13 and the fourth lens 14, and a plate glass 16 is disposed on the image side of the fourth lens 14. The imaging plane I1 is located away from the plate glass 16. The fourth lens 14 is a cemented lens including an object side lens 17 having negative power and an image side lens 18 having positive power. The object side lens 17 and the image side lens 18 are bonded by a resin adhesive, and a resin adhesive layer B <b> 1 is formed between the object side lens 17 and the image side lens 18.

  The first lens 11 is a meniscus lens in which the object side lens surface 11a protrudes toward the object side. The object side lens surface 11a and the image side lens surface 11b of the first lens 11 each have a positive curvature.

  In the second lens 12, the object side lens surface 12a has a negative curvature, and the image side lens surface 12b has a positive curvature. Therefore, the object side lens surface 12a includes a concave curved surface portion that is recessed toward the image side toward the optical axis L1, and the image side lens surface 12b is a concave surface that is recessed toward the object side toward the optical axis L1. It has a part. The object side lens surface 12a and the image side lens surface 12b are aspherical.

  In the third lens 13, the object side lens surface 13a has a positive curvature, and the image side lens surface 13b has a negative curvature. Accordingly, the object side lens surface 13a includes a convex curved surface portion protruding toward the object side toward the optical axis L1, and the image side lens surface 13b is a convex curved surface protruding toward the image side toward the optical axis L1. It has a part. The object side lens surface 13a and the image side lens surface 13b of the third lens 13 are aspherical.

  The object side lens 17 of the fourth lens 14 has an object side lens surface 17a having a positive curvature and an image side lens surface 17b having a positive curvature. Therefore, the object side lens surface 17a includes a convex curved surface portion protruding toward the object side toward the optical axis L1, and the image side lens surface 17b is a concave curved surface recessed toward the object side toward the optical axis L1. It has a part. The object side lens surface 17a and the image side lens surface 17b of the object side lens 17 are aspherical.

  The image side lens 18 of the fourth lens 14 has an object side lens surface 18a having a positive curvature and an image side lens surface 18b having a negative curvature. Accordingly, the object-side lens surface 18a includes a convex curved surface portion protruding toward the object side toward the optical axis L1, and the image-side lens surface 18b is a convex curved surface protruding toward the image side toward the optical axis L1. It has a part. The object side lens surface 18a and the image side lens surface 18b of the image side lens 18 are aspherical.

Here, the image-side lens surface 17b of the object-side lens 17 and the object-side lens surface 18a of the image-side lens 18 which are the cemented surfaces of the object-side lens 17 and the image-side lens 18 have different aspherical shapes. Yes. Further, the thickness of the resin adhesive layer B1 on the optical axis L1 is D, and the object side lens 17 at the height H at the effective diameter of the image side lens surface 17b of the object side lens 17 in the direction orthogonal to the optical axis L1. When the sag amount of the image-side lens surface 17b is Sg1H and the sag amount of the object-side lens surface 18a of the image-side lens 18 at the height H is Sg2H, the imaging lens 10 of this example has the following conditional expression (1 ) And conditional expression (2) are satisfied. The sag amount is the image side lens surface 17b of the object side lens 17 in the direction orthogonal to the optical axis L1 when a plane that includes the intersection of the lens surface and the optical axis L1 and is orthogonal to the optical axis L1 is used as a reference plane. Is the distance in the direction of the optical axis L1 from the reference surface to the lens surface at the height H at the effective diameter. FIG. 3 is an explanatory diagram of the sag amount. S1 indicates a reference surface with respect to the image side lens surface 17b of the object side lens 17, and S2 indicates a reference surface with respect to the object side lens surface 18a of the image side lens 18.
20 μm ≦ D (1)
Sg1H ≦ Sg2H (2)

  Conditional expression (1) and conditional expression (2) indicate that the resin adhesive layer between the image side lens surface 17b of the object side lens 17 and the object side lens surface 18a of the image side lens 18 which have different aspherical shapes. The thickness dimension of B1, that is, the distance between the image side lens surface 17b of the object side lens 17 and the object side lens surface 18a of the image side lens 18 which are the cemented surfaces of the two lenses constituting the cemented lens is defined. Is.

  Since the imaging lens 10 of this example satisfies the conditional expressions (1) and (2), the distance between the image side lens surface 17b of the object side lens 17 and the object side lens surface 18a of the image side lens 18 can be widened. it can. Therefore, during the bonding operation for bonding the object side lens 17 and the image side lens 18, the image side lens surface 17b of the object side lens 17 and the object side lens surface 18a of the image side lens 18 are brought into contact with each other, and each lens surface is contacted. It is possible to prevent or suppress the occurrence of damage. Further, since the distance between the image-side lens surface 17b of the object-side lens 17 and the object-side lens surface 18a of the image-side lens 18 is wide, it is easy for the resin adhesive to go around between these lens surfaces. It is possible to prevent bubbles from remaining.

Moreover, the imaging lens 10 of this example satisfies the following conditional expression (3).
D ≦ 100μm (3)

  Conditional expression (3) is for suppressing an increase in the shift of the field curvature on the tangential surface to the plus side. If the upper limit value of conditional expression (3) is exceeded, the shift of the field curvature to the plus side becomes large, and correction becomes difficult. In this example, since D = 20 μm, it is possible to correct the shift to the plus side of the curvature of field in the tangential plane by design.

Furthermore, when the radius of curvature of the image side lens surface 17b of the object side lens 17 is Rs and the focal length of the entire lens system is f, the imaging lens 10 of the present example satisfies the following conditional expression (4).
0.9 ≦ Rs / f ≦ 1.3 (4)

  If the lower limit of conditional expression (4) is not reached, the curvature of the image side lens surface 17b of the object side lens 17 becomes large, so that it is not easy to join the image side lens 18, and workability of joining the cemented lens is reduced. To do. On the other hand, if the upper limit value of conditional expression (4) is exceeded, it will be difficult to correct chromatic aberration. In this example, since Rs / f = 1.077, it is easy to join the cemented lens, and the chromatic aberration is corrected well.

Further, when the focal length of the entire lens system is f, the focal length of the object side lens 17 is f41, and the focal length of the image side lens 18 is f42, the imaging lens 10 of this example has the following conditional expression (5) Meet.
−3.0 ≦ (f41 / f42) /f≦−1.5 (5)

  If the lower limit of conditional expression (5) is not reached, it will be difficult to balance axial chromatic aberration and lateral chromatic aberration, resulting in a decrease in the resolution of the peripheral portion of the image. If the upper limit value of conditional expression (5) is exceeded, it will be difficult to correct chromatic aberration. In this example, (f41 / f42) /f=−1.54, so that a reduction in resolution can be suppressed and chromatic aberration can be corrected well.

Here, in the imaging lens 10 of this example, when the radius of curvature of the object side lens surface 13a of the third lens 13 is R31 and the radius of curvature of the image side lens surface 13b of the third lens 13 is R32, R3
1 = 3.573 and R32 = −5.766, which satisfies the following conditional expression (6).
R31 ≦ | R32 | (6)

  In the imaging lens 10 of this example, the Abbe number of the first lens 11, the second lens 12, and the image side lens 18 is 40 or more, and the Abbe number of the third lens 13 and the object side lens 17 is 31 or less. Thus, chromatic aberration is corrected.

The F number of the imaging lens 10 of this example is set to Fno. When the half angle of view is ω and the total length of the lens system is L, these values are as follows.
Fno. = 2.0
ω = 99.4 °
L = 16.089mm

The focal length of the entire lens system is f, the focal length of the first lens 11 is f1, the focal length of the second lens 12 is f2, the focal length of the third lens 13 is f3, and the focal length of the fourth lens 14 is f4. When the focal length of the object side lens 17 is f41 and the focal length of the image side lens 18 is f42, these values are as follows.
f = 1.155mm
f1 = −8.193 mm
f2 = −2.685mm
f3 = 4.126mm
f4 = 3.275mm
f41 = −3.351 mm
f42 = 1.85mm

  Next, Table 1 shows lens data of each lens surface of the imaging lens 10. In Table 1, each lens surface is specified in the order counted from the object side. The lens surface marked with an asterisk is aspheric. The 7th surface is the diaphragm 15, and the 12th and 13th surfaces are the object side glass surface and the image side glass surface of the plate glass 16. The unit of curvature radius and spacing is millimeters. Note that the values of Nd (refractive index) and νd (Abbe number) of the 10 surfaces indicate the values of the resin adhesive layer B1.

  Next, Table 2 shows aspherical coefficients for defining the aspherical shape of the aspherical lens surface. Also in Table 2, each lens surface is specified in the order counted from the object side.

  The aspherical shape adopted for the lens surface is such that Y is the sag amount, c is the reciprocal of the radius of curvature, K is the cone coefficient, h is the ray height, 4th order, 6th order, 8th order, 10th order, 12th order, When the 14th and 16th order aspherical coefficients are A4, A6, A8, A10, A12, A14, and A16, respectively, they are expressed by the following equations.

According to such an imaging lens 10, the following effects can be obtained.
4A to 4D are a longitudinal aberration diagram, a lateral aberration diagram, a field curvature diagram, and a distortion diagram of the imaging lens 10. In the longitudinal aberration diagram of FIG. 4A, the horizontal axis indicates the position where the light beam intersects the optical axis L1, and the vertical axis indicates the height at the pupil diameter. In the lateral aberration diagram of FIG. 4B, the horizontal axis indicates the entrance pupil coordinates, and the vertical axis indicates the amount of aberration. 4A and 4B show simulation results for a plurality of light beams having different wavelengths. In the field curvature diagram of FIG. 4C, the horizontal axis indicates the distance in the direction of the optical axis L1, and the vertical axis indicates the height of the image. In FIG. 4C, S represents the field curvature aberration on the sagittal surface, and T represents the field curvature aberration on the tangential surface. In the distortion diagram of FIG. 4D, the horizontal axis indicates the amount of image distortion, and the vertical axis indicates the height of the image.

  As shown in FIG. 4A, according to the imaging lens 10 of this example, the axial chromatic aberration is corrected well. Further, as shown in FIG. 4B, color bleeding is suppressed. Further, as shown in FIGS. 4A and 4B, both axial chromatic aberration and lateral chromatic aberration are corrected in a balanced manner in the peripheral portion. Furthermore, as shown in FIG. 4C, according to the imaging lens 10 of the present example, the field curvature is corrected well. Therefore, the imaging lens 10 has a high resolution.

  Here, in this example, the imaging lens 10 is designed such that the distance on the optical axis L1 between the image side lens surface 17b of the object side lens 17 and the object side lens surface 18a of the image side lens 18 is 20 μm or more in advance. Therefore, at the time of design, it is possible to consider the shift to the plus side of the curvature of field on the tangential surface, which occurs when the resin adhesive layer B1 becomes thick. Therefore, according to the imaging lens 10 of the present example, as shown in FIG. 4C, the shift of the field curvature on the tangential surface to the plus side is suppressed.

  Next, FIG. 5 is a spherical aberration diagram of the imaging lens 10, and a solid line indicates spherical aberration with respect to a light beam having a wavelength of 588 nm (visible light beam). A dotted line indicates spherical aberration with respect to a light ray having a wavelength of 850 nm (near infrared ray). The horizontal axis of the spherical aberration diagram is the position where the light beam intersects the optical axis, and the vertical axis is the height at the pupil diameter. As shown in FIG. 5, in the imaging lens 10, spherical aberration with respect to a light beam having a wavelength of 850 nm is corrected, and it is not necessary to perform focusing when photographing under visible light and when photographing under near infrared rays. That is, in the imaging lens 10 of the present example, it is possible to suppress occurrence of a focus shift between shooting using visible light and shooting using near infrared rays. In the case where the fourth lens 14 is composed of a single lens that is not a cemented lens, both spherical aberration for a light beam having a wavelength of 588 nm (visible light) and spherical aberration for a light beam having a wavelength of 850 nm (near infrared light) are balanced. It is difficult to correct well so that no out-of-focus occurs between photographing using visible light and photographing using near infrared rays.

  The imaging sensor (image sensor) 1 includes, for example, a sensor body 114 which is a CCD (Charge Coupled Device) image sensor, and red (R), green (G), and blue (B) corresponding to each pixel of the sensor body 114. And a color filter 113 in which infrared (IR) regions (filters of respective colors) are arranged in a predetermined arrangement.

  The sensor main body 114 is a CCD image sensor, and a photodiode as a light receiving element is disposed in each pixel. The sensor main body 114 may be a CMOS (Complementary Metal Oxide Semiconductor) image sensor instead of the CCD image sensor.

  The sensor main body 114 is provided with a color filter 113. Here, a Bayer array color filter that has red R, green G, and blue B regions but no infrared IR region has 16 regions of 4 × 4 in length, which is a basic pattern. Each region is a G region, four regions are R, and four regions are B. On the other hand, as shown in FIG. 6, the color filter 113 according to the present embodiment has four R out of four G regions in the Bayer array as IR regions. G is 4, B is 4, IR is 4. Note that the color filter including the IR region is not limited to the color filter 113 illustrated in FIG. 6, and various color filters can be used. However, it is necessary to include both the visible light color region and the IR region. Each RGB region is a general RGB filter, but has a transmittance peak in the wavelength range of each color and transparency in the near-infrared wavelength region. The R region was R + IR, the green region was G + IR, and the blue region was B + IR.

  The transmittance spectra of the R region, the G region, and the B region in the present embodiment are as shown in the graph of FIG. That is, the transmittance spectrum of each of the red (R), green (G), blue (B), and infrared (IR) filters of the color filter 113 is shown, the vertical axis indicates the transmittance, and the horizontal axis indicates the transmittance. It is a wavelength. The wavelength range in the graph includes a part of the visible light band and the near-infrared band, and indicates a wavelength range of 300 nm to 1100 nm, for example.

  For example, as shown by R (double line) in the graph, the R region has a substantially maximum transmittance at a wavelength of 600 nm, and the long wavelength side maintains a substantially maximum transmittance even when the wavelength exceeds 1000 nm. It will be in the state. The G region has a peak at which the transmittance is maximized at a portion where the wavelength is about 540 nm, and the transmittance is minimized at a portion of about 620 nm on the long wavelength side, as indicated by G (broken line having a wide interval) in the graph. There is a part that becomes. In the G region, the longer wavelength side tends to increase from the portion where the transmittance is minimized, and the transmittance is substantially maximum at about 850 nm. On the longer wavelength side, the transmittance is substantially maximum even when the wavelength exceeds 1000 nm. The region B has a peak at which the transmittance is maximized at a portion where the wavelength is about 460 nm, as shown by B (dashed broken line) in the graph, and is transmitted at a portion around 630 nm on the long wavelength side. There is a part where the rate is minimal. Further, the longer wavelength side tends to increase, and the transmittance is substantially maximized at about 860 nm. On the longer wavelength side, the transmittance is substantially maximized even if it exceeds 1000 nm. The IR region blocks light on the short wavelength side from about 780 nm, blocks light on the long wavelength side from about 1020 nm, and the portion of about 820 nm to 920 nm has a substantially maximum transmittance.

  The transmittance spectrum in each of the R, G, B, and IR regions is not limited to that shown in FIG. 7, but the color filter 113 that is currently used generally has a transmittance spectrum close to this. It seems to show. Note that 1 on the vertical axis indicating the transmittance does not mean that 100% of the light is transmitted, but in the color filter 113, for example, indicates the maximum transmittance.

The DBPF 111 has a transmission characteristic in the visible light band, has a cutoff characteristic in the first wavelength band adjacent to the long wavelength side of the visible light band, and is a second wavelength band that is a part of the first wavelength band. Is an optical filter having transmission characteristics. As shown in FIG. 1, when the DBPF 111 is provided between the imaging lens 10 and the imaging sensor 115 including the color filter 113, the DBPF 111 is provided on the imaging lens 10 side of the imaging sensor 115 even if provided on the image side of the imaging lens 10. May be. Further, it may be provided on the object side of the imaging lens 10.
As shown in the graph of FIG. 7, the DBPF 111 has a visible light band indicated by DBPF (VR) and a DBPF at a position slightly away from the visible light band on the long wavelength side, as indicated by DBPF (solid line) in the graph. The transmittance of two bands of the infrared band (second wavelength band) indicated by (IR) is high. Further, DBPF (VR) as a band having a high transmittance in the visible light band has a wavelength band of about 370 nm to 700 nm, for example. Further, DBPF (IR) as the second wavelength band having a high transmittance on the infrared side is, for example, a band of about 830 nm to 970 nm.

In the present embodiment, the relationship between the transmittance spectrum of each region of the color filter 113 and the transmittance spectrum of the DBPF 111 is defined as follows.
That is, the DBPF (IR), which is the second wavelength band that transmits infrared light in the transmittance spectrum of the DBPF 111, has an approximately maximum transmittance in each of the R region, the G region, and the B region. It is included in the wavelength band A shown in FIG. 7 where the transmittance is substantially the same in the region, and is included in the wavelength band B that transmits light at the substantially maximum transmittance in the IR region.

Here, the wavelength band A in which the transmittance in each of the R, G, and B regions is substantially the same is a portion where the transmittance difference in each region is 10% or less.
Note that, on the shorter wavelength side (wavelength band C) than the wavelength band A, the transmittance of the G and B regions is lower than the R region where the transmittance is substantially maximum. In DBPF 111, the portion where the transmittance of each region of R, G, and B is different is DBPF (VR), which is a portion having high transmittance in the visible light band, and the second wavelength band in the infrared light band. This corresponds to a portion where the transmittance that substantially blocks the light of the DBPF 111 between the portion having a high transmittance and DBPF (IR) is minimized. That is, on the infrared side, the transmission of light in a portion where the difference in transmittance between the R, G, and B regions is large is cut, and the transmittance in each region is substantially maximized on the longer wavelength side. The light is transmitted in the wavelength band A in which are substantially the same.

  From the above, in the present embodiment, DBPF 111 used in place of the infrared light cut filter has a region that transmits light not only in the visible light band but also in the second wavelength band on the infrared light side. Therefore, in color imaging with visible light, it is affected by light that has passed through the second wavelength band, but the second wavelength band has different transmittances in the R, G, and B regions as described above. A portion of light is not transmitted, and only the light in the wavelength band in which the transmittance of each region is substantially maximized and becomes substantially the same transmittance is transmitted.

  Further, in the second wavelength low band of the DBPF 111, light of a portion where the transmittance is substantially maximum in the IR region is transmitted. Therefore, when it is assumed that R, G, B, and IR regions are respectively provided in four pixels that are very close to each other and irradiated with substantially the same light, in the second wavelength band, the R region, G The light passes substantially the same in the region B, the region B, and the IR region, and as light on the infrared side, substantially the same amount of light in each region including IR This leads to a photodiode. That is, the amount of light that passes through the second wavelength band on the infrared side of the light that passes through the R, G, and B filters is the same as the amount of light that passes through the IR region. When assumed as described above, the output signal of the assumed pixel from the sensor main body 114 that has received light that has basically passed through the R, G, and B filters and the IR filter as described above have passed. The difference from the output signal of the assumed pixel from the sensor main body 114 that has received the light as described above is that each of the R, G, and B cut off the infrared light that has passed through the R, G, and B regions. It becomes the output signal of the visible light part.

  Actually, as shown in the pattern of the color filter 113, any one region of R, G, B, and IR is arranged for each pixel of the sensor body 114, and each color irradiated to each pixel. For example, in each pixel, the luminance of each color of each pixel is obtained by using a well-known interpolation method (interpolation method) in each pixel. Differences between the luminance of the R, G, and B pixels and the interpolated IR luminance can be set as the luminances of R, G, and B, respectively. Note that the image processing method for removing the infrared light component from the luminance of each color of R, G, B is not limited to this, and finally passes through the second wavelength band from each luminance of R, G, B. Any method may be used as long as it can cut the influence of light. In any of the methods, the DBPF 111 cuts a portion where the transmittance of the R, G, B region on the infrared side is different from 10%, that is, a portion where the transmittance is different from a predetermined ratio. Processing that removes the influence of infrared light becomes easy.

  When infrared light photographing is used as night photographing, the amount of light is insufficient at night as in the case of visible light, so infrared light illumination is necessary. The transmittance spectrum of DBPF 111 shown in FIG. 7 takes into account the transmittance spectrum of each region of R, G, B, and IR and the light emission spectrum of infrared light, for example, an infrared light LED for illumination. decide.

  In such an image sensor, the second wavelength band that transmits light on the infrared side of the DBPF 111 is on the infrared side of each of the R, G, B, and IR regions, and the transmittance of each region is substantially maximum. Thus, it is included in the wavelength band A in which the transmittance in each region is substantially the same, and is included in the wavelength band B in which the transmittance in the IR region is substantially maximum. In other words, on the longer wavelength side than the visible light band, the transmittance of each of the R, G, and B filters is substantially maximum only in the R region, and the transmittance in the G and B regions is not substantially maximum. As a result, the transmittances of the R, G, and B regions are not substantially the same, but different portions of light are cut by the DBPF 111.

  That is, in each of the R, G, B, and IR regions, light in the second wavelength band is transmitted on the infrared side, so that the infrared side transmittance in each region is substantially the same. If the light having the same wavelength band is irradiated with the same light amount, the transmitted light amounts in the R, G, B, and IR regions are the same. Thus, as described above, the color based on the output signal from the pixel corresponding to each of the R, G, and B regions is corrected, and the influence of the infrared light passing through the second wavelength band of the color at the time of color photographing is affected. A suppressed image can be easily obtained.

  Further, by making the second wavelength band correspond to the peak of the emission spectrum of the infrared light illumination included in the wavelength band A and the wavelength band B described above, the light of the infrared light illumination can be used efficiently, The width of the second wavelength band can be narrowed to reduce the influence of infrared light passing through the second wavelength band during color photography.

  That is, by using the DBPF 111, highly accurate correction can be performed by subtracting the value of each IR signal from the value of each RGB signal of the image sensor 115. For example, the light receiving components of the pixels of each color of the imaging sensor 115 are in a state in which an IR component is added to the components of each color as shown below.

R pixel R + IR
G pixel G + IR
B pixel B + IR
IR pixel IR

  Therefore, as shown below, IR correction is performed by removing the IR component from the light receiving components of the RGB pixels excluding the IR pixels.

R signal (R pixel output)-(IR pixel output) = (R + IR) -IR = R
G pixel (R pixel output)-(IR pixel output) = (G + IR) -IR = G
B pixel (R pixel output)-(IR pixel output) = (B + IR) -IR = B
As a result, IR components that pass through the DBPF 111 and pass through the color filter can be excluded from the regions of each color other than the IR of the color filter.

In the signal processing unit 116, the synchronization process (interpolation process) is performed as described above, and in the image data as a moving image, in each frame, all pixels are R frames, G frames, B frames, IR Frames are generated. That is, in the color filter, there are only four R, G, B, and IR pixels in the 4 × 4 basic pattern described above, but this is interpolated by interpolation processing, and all the pixels of the basic pattern are R An image, a G image, a B image, and an IR image are generated.
Also. The signal processing unit 116 performs image processing such as gamma correction, white balance, and RGB matrix correction as described above.

  The signal processing unit 116 outputs a visible image signal 121 composed of RGB signals from which IR components have been removed and an infrared image signal 122 composed of IR signals. The visible image signal 121 is output to the visible image processing unit 117. The visible image processing unit 117 performs face detection (face recognition) by image recognition processing. The face detection is performed by a known process.

  An image processing and image recognition program can be easily created using Intel (registered trademark) Open CV (Intel Open Source Computer Vision Library). For example, when creating a face recognition program, an object detection program registered in the open CV can be used. As a principle of image recognition, there are a learning phase and a recognition phase. By extracting a feature amount from an image and learning a feature of an object by a learning algorithm, for example, image recognition such as face recognition becomes possible. In Open CV, Haar / Like feature values are used as image feature values, and an algorithm called Adaboost is used as a learning algorithm. In the object detection program, it is possible to recognize a face image as a face in the object detection program by causing the object detection program to perform machine learning based on the feature points. Note that the open CV is not necessarily used for the image recognition program, and an existing program or a chip equipped with an existing image recognition circuit may be used.

  The visible image processing unit 117 recognizes the face, detects a region where the skin of the recognized face is exposed (skin region), and outputs the coordinate position in each frame of the moving image data to the infrared image processing unit 118. To do. In the face detection, when there are a plurality of persons 101 within the imaging range (within a frame), a plurality of faces are detected simultaneously. When the plurality of faces are recognized, the coordinate positions on the frames of the plurality of skin regions of the recognized faces are sent to the infrared image processing unit 118, respectively. The visible image processing unit 117 outputs a visible image signal to the monitor 120 and displays the visible image on the monitor 120.

Note that the visible image signal 121 may be input from the signal processing unit 116 to the monitor 120.
An infrared image signal is input to the infrared image processing unit 118 for each frame from the signal processing unit 116, and the position of the skin region of each frame obtained as described above is input from the visible image processing unit 117. . The infrared image processing unit 118 identifies the coordinate position of the skin region on the frame of the infrared image. Note that the skin region input from the visible image processing unit 117 may be, for example, a square or rectangular region with a predetermined number of pixels in the vertical and horizontal directions, or a circular region with a radius specified by the number of pixels.

  The infrared image processing unit 118 calculates, for example, the sum or average of the infrared signals of each pixel in the skin region of each frame. The sum or average of the output levels (intensities) of the portions determined as skin areas in each frame of the infrared image signal is as shown in the graph of FIG. 8, for example. The output level of external light is shown, and the horizontal axis is the number of frames. In this example, the image is captured at 30 fps, and 30 frames are 1 second.

  The skin has capillaries on its surface layer, and the capillaries are repeatedly expanded and contracted in accordance with the heartbeat. In this case, when the capillaries expand, the amount of blood per unit area of the skin increases, and hemoglobin contained in blood red blood cells increases. When the capillary result shrinks, the blood volume per unit area of the skin decreases and the blood hemoglobin decreases. Hemoglobin is also known to absorb near-infrared light. When skin hemoglobin increases, near-infrared light reflection decreases, and when skin hemoglobin decreases, near-infrared light reflection decreases. To increase.

  Therefore, as shown in FIG. 8, the reflected light amount (intensity) of the skin region of the infrared image is such that, for example, a small wave corresponding to a pulse rate of about 50 to 150 per minute is combined with the infrared image. It has become. In the graph of FIG. 8, large fluctuations in the waves indicate fluctuations in the brightness of the infrared light in the skin region of the infrared image, and small waves indicate an increase or decrease in the reflected infrared light corresponding to the pulse. It should be noted that if the person 101 photographed and face-recognized does not move and the illumination is constant, the amount of reflected infrared light may not vary greatly.

  Since an infrared image of the skin region is in a state where a wave having a frequency corresponding to the pulse rate is synthesized, a known process is performed on the wave having a frequency corresponding to the pulse rate. For example, the Fourier transform can clarify a sine wave group that is a component of a distorted waveform as a synthesized wave. By using this, the sine wave component constituting the input waveform can be extracted by performing discrete Fourier transform from the reflection intensity of the infrared light of the skin region of each frame described above.

  The waveform corresponding to the pulse rate extracted from the waveform shown in FIG. 8 is shown in the graph of FIG. The vertical axis represents the infrared reflection intensity after extraction, and the horizontal axis represents the number of frames described above. The number of peaks per unit time of the waveform shown in FIG. 9, for example, per minute is the pulse rate. Note that it is not necessary to use image data having a length of one minute of infrared image data to calculate the pulse rate. For example, the pulse rate is detected from a wave extracted for several seconds to several tens of seconds. .

  In addition, the infrared image processing unit 118 detects the body temperature from the infrared intensity of the skin region described above. In the body temperature measurement, it is preferable to calibrate by photographing the skin of the person 101 whose body temperature is known. In the body temperature detection, it is not always necessary to measure the absolute body temperature. For example, the temperature relative to an infrared image of the past skin that has already been taken or an infrared image of the skin that has been taken at the same time. The person 101 having a high value may be detected. Further, a temperature difference with respect to a predetermined background portion without the person 101 may be detected.

  The pulse rate and body temperature (or temperature difference) measured by the infrared image processing unit 118 are output to the abnormality determination unit 119. In the abnormality determination unit, for example, the upper and lower limits of a predetermined normal range of pulse rate are stored, and an abnormality is detected when the measured pulse rate exceeds the upper limit value or less than the lower limit value. Determined. Moreover, the upper limit and lower limit values of a predetermined normal range of body temperature or temperature difference (relative temperature) as described above are stored, and when the measured body temperature (temperature difference) exceeds the upper limit value, If it is less than the value of, it is determined to be abnormal.

Based on the processing of the visible image processing unit 117, a visible image based on the visible image signal is displayed on the monitor 120, and at least one of the pulse rate and body temperature is determined to be abnormal by the person 101 whose face is recognized. A display that can specify the person 101 is performed.
Here, for example, as shown in FIG. 10, identification image data including the line surrounding the face (head) of the person 101 determined to be abnormal, and the pulse rate (BP) and body temperature (BT: temperature difference) are displayed. It has become so.

  Based on the image of the monitor 120, a staff member such as a guard can identify and respond to the person 101 whose pulse rate or body temperature is determined to be abnormal. Even if control is performed so that the imaging range of the surveillance camera can be rotated to the left and right, and the skin area determined to be abnormal as described above is moved to the center of the left and right of the frame as described above. Good.

  Next, image processing performed in such an imaging system will be described with reference to the flowchart of FIG. First, the RGB visible image signal 121 from which the infrared component is removed from the camera 110 as described above, and the infrared image signal 122 are captured by the visible image processing unit 117, the infrared image processing unit 118, and the abnormality determination unit 119. Input to the part of the system 100 that performs image processing (step S10). That is, the visible image signal is input to the visible image processing unit 117, and the infrared image signal is input to the infrared image processing unit 118.

  Next, the visible image processing unit 117 performs face detection as described above (step S20). In addition, the infrared image processing unit 118 detects the input infrared image signal, and the visible image processing unit 117 performs face detection. From the detected position (range) of the skin region, the pulse rate and body temperature are detected as described above (step S30). The detected pulse rate and body temperature are determined by the abnormality determination unit 119 as to whether or not they are abnormal as described above (step S40). If there is an abnormality, for example, it is output to the monitor 120 as described above (step S50).

Such an imaging system includes the DBPF 111 and the color filter 113 having an infrared region as described above, and the signal processing unit 116 that removes the infrared component from the visible image. Thus, the visible image signal 121 from which the infrared component is removed and the infrared image signal that is not cut by the infrared cut filter can be obtained simultaneously.
Therefore, it is possible to manufacture an imaging system capable of detecting a face from a visible image and measuring the pulse rate and body temperature in substantially real time from the position of the detected skin area of the face and an infrared image at a low cost.

  In addition, by using the imaging lens 10 as described above, even if a visible image having a large wavelength difference between the wavelength bands and an infrared image are simultaneously captured by one optical system, the person 101 as a subject is captured. On the other hand, it is possible to take a picture in a state where there is substantially focus in both visible and infrared.

  Further, since the pulse as a vital sign is detected by an infrared image, for example, in a place where the infrared light is insufficient, the second wavelength band of the DBPF 111 and the red color filter 113 are used. You may illuminate using LED etc. of the infrared light which has a peak in the wavelength which permeate | transmits both the wavelength range | bands which pass an outer area | region. In this case, since the illumination light cannot be seen by the person 101 as the subject of photographing, the pulse measurement using infrared light is not realized.

  From the above, it is possible to perform measurement of the pulse rate and the like using a visible image and an infrared image with one imaging camera 110. At this time, one optical system, one imaging element, Although the DBPF 111 is used, but no infrared cut filter is used, the imaging camera 110 can be manufactured more compactly and at a lower cost.

Next, a second embodiment of the present invention will be described.
In the second embodiment, an imaging lens 10A shown in FIG. 12 as an optical system of the imaging camera 110 of the imaging system 100 is different from the imaging lens 10 described above. The configuration other than the imaging lens 10 </ b> A is the same as that of the first embodiment. The imaging lens 10 </ b> A will be described, and the description of the other configuration of the imaging system 100 will be omitted.

  In the present embodiment, the light beam in the visible light band is focused at the position where the infrared light transmitted through the second wavelength band of the DBPF 111 and the IR region of the color filter 113 is focused using the hologram 21. By matching with the focal position, it is possible to focus on visible light and infrared light simultaneously.

In the hologram 21, for example, it is known that it can function as an optical element such as a lens and a concave mirror only for light in a specific narrow wavelength range, and development for using the hologram 21 as an optical element has been performed. Yes.
It is known that such a hologram 21 has wavelength selectivity and wavefront reproducibility. The wavelength selectivity is, for example, a property that affects only light in a specific narrow wavelength range and hardly affects light outside the wavelength range.

  The hologram 21 is produced by a two-beam interference method in which two light beams of the object light (light reflected from the object) and the reference light are interfered and the interference fringes are recorded on the photosensitive material. Thus, for example, when the reference light is applied as illumination light to the hologram 21 at the same incident angle as that at the time of creation, the above-described object light is reproduced (reproduced). The hologram 21 is known to have the highest diffraction efficiency when reproducing illumination is performed with light having the same wavelength and incident angle as the light used for production. For example, in the case of a reflection hologram, it is possible to reflect light having a wavelength used at the time of creation and transmit light having other wavelengths.

  Further, the hologram 21 has wavefront reproducibility as described above. Here, for example, at the time of creating a hologram, parallel light is irradiated as reference light, and light that is being condensed by a condensing lens or a concave mirror is used as object light on the surface irradiated with the reference light of the hologram using a half mirror (for example, When the interference fringes are recorded by causing the reference light and object light to interfere with each other by irradiating a spherical wave, the created hologram functions as a lens that condenses the illumination light that is parallel light (converts it into a spherical wave). To do.

  In the present embodiment, using the characteristics of the hologram 21 as described above, for example, infrared light having a wavelength of 850 nm is used as reference light and object light at the time of creation, and the above-described concave mirror or lens is used for visible light. The hologram 21 is created using an optical element that corrects a focus shift due to chromatic aberration of infrared light. In creating the hologram 21, the hologram 21 is not only exposed to light by actually causing the two light beams to interfere as described above, but the interference fringes are obtained by computer simulation and the interference fringes are baked on the photosensitive material. (Printed).

In such a hologram 21, for example, when infrared light that passes through the second wavelength band of the DBPF 111 and passes through the IR region of the color filter 113 is transmitted, its direction is changed, but visible light Even if it passes through the hologram 21, its direction hardly changes. Hereinafter, an imaging lens 10A including such a hologram 21 will be described.

  As shown in FIG. 12, the imaging lens 10 </ b> A matches the position where the light beam having the infrared wavelength of 850 nm is focused with the focal position where the light beam in the visible light region is focused by the hologram 21. When imaging with infrared is simultaneously performed with one image sensor as described above, it is possible to achieve a state in which both visible light and infrared light are in focus.

  The imaging lens 10A is a wide-angle lens having an angle of view of 172.6 °, and the front group lens I having a negative power and the rear group lens II having a positive power from the object side toward the imaging surface 22 are arranged in this order. It has an arranged configuration. The front group lens I and the rear group lens II are each composed of two lenses. More specifically, the front lens group I includes a first concave lens 23 and a second concave lens 24, which are meniscus lenses having a convex surface facing the object side. The rear lens group II is composed of one front lens 25 and one rear lens 26. A diaphragm 27 is disposed between the front lens 25 and the rear lens 26, and a hologram 21 is disposed in the vicinity of the imaging side of the diaphragm 27. In the present invention, when two or more concave lenses are continuously arranged from the object side, the two lenses from the object side are grasped as the front group lens I. When there is one concave lens from the object side and the second lens is not a concave lens, this single concave lens is grasped as the front lens group I.

  The hologram 21 has a positive power and a maximum diffraction efficiency with respect to a light beam having a wavelength of 850 nm. As the hologram 21, either a volume hologram or a relief hologram can be used. A cover glass 28 is disposed between the rear lens 26 and the imaging plane 22. Lens surfaces 24a and 24b on both sides of the second concave lens 24 of the first lens group I, lens surfaces 25a and 25b on both sides of the front lens 25 of the second lens group II, and lens surfaces 26a on both sides of the rear lens 26, Reference numeral 26b denotes an aspherical surface.

The lens data of the entire optical system of the imaging lens 10A is as follows.
F number: 2.4
Focal length f: 1.495mm (all systems)
fH: 22 mm (hologram 21)
f1: -5.77 mm (first concave lens 23)
f2: -2.50 mm (second concave lens 24)
f3: 2.50 mm (front lens 25)
f3: 3.10 mm (rear lens 26)
f12: -1.41 mm (front lens group I)
f23: 3.07 mm (rear group lens II)
Angle of view: 172.6 °
In the present embodiment, the reference wavelength W1 of the light in the visible light region is set to 500 nm, and the focal length of the entire system of the imaging lens 10A is relative to the reference wavelength W1. The focal length fH of the hologram 21 is for an infrared ray having a specific wavelength W2 of 850 nm.

  Table 3 shows lens data of each lens surface of the imaging lens 10A, and Table 4 shows aspheric coefficients for defining the aspheric shape of the aspheric lens surface. In Table 3, i represents the order of the lens surfaces counted from the object side, R represents the curvature of the lens surfaces, D represents the distance of the lens surfaces, Nd represents the refractive index of each lens, and νd represents each lens. Represents the Abbe number. Further, S indicates the diaphragm surface, H indicates the hologram surface, and * indicates that the lens surface is an aspherical surface.

Here, the aspherical shape adopted for the lens surface is that the axis in the optical axis direction is X, the height in the direction orthogonal to the optical axis is H, the conical coefficient is K, the aspherical coefficients are A, B, C, D, Assuming E, F, and G, they can be expressed by the following equations.

The imaging lens 10A has a reference wavelength W1 (500 nm) of a light ray in the visible light region, a specific wavelength W2 (850 nm), a focal length of the entire system with respect to the reference wavelength f (1.495 mm), and a focal point of the hologram 21 with respect to the specific wavelength. When the distance is fH (22 mm), the following formula is satisfied.
6 <| fH / f | / (W2 / W1) ≦ 14
That is, in the imaging lens 10A, the value of the conditional expression is 8.9.

  13A to 13D are a spherical aberration diagram, a lateral aberration diagram, a white MTF (Modulation Transfer Function) graph, and an infrared MTF graph, respectively, in the imaging lens 10A. In the spherical aberration diagram of FIG. 13A, the horizontal axis is the position where the light beam intersects the optical axis, and the vertical axis is the height at which the light beam enters the optical system. FIG. 13A shows that the spherical aberration is corrected for a light ray having a wavelength of 850 nm in the infrared region. FIG. 13B is a lateral aberration diagram on the meridional surface and the sagittal surface at each angle of view. The horizontal axis represents the entrance pupil coordinates, and the vertical axis represents the lateral aberration. FIG. 13B shows that the lateral aberration with respect to a light ray having a wavelength of 850 nm in the infrared region is corrected at each angle of view. In each MTF graph of FIGS. 13C and 13D, the horizontal axis represents the spatial frequency and the vertical axis represents the contrast. FIG. 13 (d) shows that a decrease in contrast due to an increase in spatial frequency is suppressed during imaging under light in the infrared region.

In such an optical system of the imaging lens 10A, the focal length of infrared light (wavelength 850 nm) is 1.463 mm, and the focal length of visible light (reference wavelength 500 nm) is 1.495 mm, which are almost the same. ing.
By using such an imaging lens 10A, as in the case of the first embodiment, it is possible to focus both when a visible image and an infrared image are simultaneously captured with one optical system. It becomes. That is, it is possible to prevent one of the visible image and the infrared image from being out of focus.

  The embodiments of the present invention have been described above with reference to the drawings. However, the specific configuration is not limited to these embodiments, and various modifications can be made without departing from the spirit of the present invention. Changes are also included.

B1 Resin adhesive layer 10 Imaging lens (optical system)
10A Imaging lens (optical system)
DESCRIPTION OF SYMBOLS 11 1st lens 12 2nd lens 13 3rd lens 14 4th lens 17 Object side lens 18 Image side lens 21 Hologram 100 Imaging system 111 DBPF (optical filter)
113 Color Filter 114 Image Sensor Body 115 Image Sensor 116 Signal Processing Unit (Signal Processing Means)
117 Visible image processing unit (visible image processing means)
118 Liquid image processing unit (infrared image processing means)
121 Visible Image Signal 122 Infrared Image Signal IR First Wavelength Band DBPF (IR) Second Wavelength Band DBPF (VR) Visible Light Band

Claims (5)

An imaging sensor comprising an image sensor main body in which a light receiving element is arranged for each pixel, and a color filter in which a plurality of visible light regions and an infrared light region are arranged in each pixel of the image sensor main body in a predetermined arrangement When,
An optical system having a lens for connecting an image on the imaging sensor;
A transmission characteristic in the visible light band, a cutoff characteristic in the first wavelength band adjacent to the long wavelength side of the visible light band, and a second wavelength band that is a part of the first wavelength band; An optical filter having transmission characteristics;
Based on the signal output from the imaging sensor, a process of subtracting the infrared light component signal from the visible light component signal is performed to obtain a visible image signal and an infrared image signal in the same imaging range. Signal processing means capable of outputting simultaneously;
Visible image processing means for specifying a region of a human face in the image of the visible image signal;
Infrared image processing means for measuring at least a part of a vital sign from an image of a region of the face of the person specified by the visible image processing means in the image of the infrared image signal system. The optical system includes, in order from the object side to the image side, a first lens having negative power, a second lens having negative power, a third lens having positive power, and a first lens having positive power. It consists of 4 lenses,
The fourth lens is a cemented lens including an object side lens having a negative power and an image side lens having a positive power, and a resin adhesive layer that bonds the object side lens and the image side lens. Prepared,
The image side lens surface of the object side lens and the object side lens surface of the image side lens have different aspherical shapes, respectively.
The thickness of the resin adhesive layer on the optical axis is D, and the image side lens of the object side lens at the height H at the effective diameter of the image side lens surface of the object side lens in the direction orthogonal to the optical axis. When the sag amount of the surface is Sg1H and the sag amount of the object side lens surface of the image side lens at the height H is Sg2H, the following conditional expressions (1) and (2) are satisfied. The imaging system according to claim 1.
20 μm ≦ D (1)
Sg1H ≦ Sg2H (2)   The optical system has a position where the infrared light passing through the second wavelength band of the optical filter and the infrared light region of the color filter is focused, and a light beam in the visible light band is focused. The imaging system according to claim 1, further comprising a hologram that matches a focal position to be connected.   The imaging system according to any one of claims 1 to 3, wherein the vital sign is a pulse and / or a body temperature.   The at least two of the signal processing means, the visible image processing means, and the infrared image processing means are constituted by an electronic circuit on one chip and are made into one chip. The imaging system according to claim 4.