JP2017195569A - Monitoring system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow for remote monitoring even in the night, by using a small and inexpensive sensor having a large number of pixels, and a light source suitable for lighting, and performing lighting and shooting simultaneously with small configuration.SOLUTION: A monitoring system 1 has a wide-angle taking lens 11, an imaging sensor 4, a laser light source 2, and a lighting optical system 3. The imaging sensor 4 has sensitivity in at least one wavelength region of visible light and near infrared light, and taking a picture of a shooting target at a position separated by a distance of 100-300 m, via the wide-angle taking lens 11. The laser light source 2 emits laser light having an intensity peak in a wavelength region where the imaging sensor 4 has sensitivity. The wide-angle taking lens 11 also serves as a part of the lighting optical system 3. The lighting optical system 3 has a laser light scanning mechanism 14 for shifting the lighting position of laser light lighting via the wide-angle taking lens 11, in order, by scanning the laser light emitted from the laser light source 2 and incident on the wide-angle taking lens 11.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a monitoring system that photographs and monitors an object using, for example, a camera.

  Conventionally, as a system for photographing an object using a camera, there are those disclosed in Patent Documents 1 to 4, for example. The system of Patent Document 1 obtains information such as the density distribution of aerosol in the atmosphere easily and with relatively high reliability by illuminating and photographing fine particles in space with a pulse laser. In this system, a light projecting system (including an illumination unit that emits a pulse laser) and a light receiving system (including a photoelectric sensor for detecting the operation of the pulse laser) are arranged tens of kilometers apart, and the pulse laser is scanned. While taking pictures of fine particles in the space.

  In Patent Document 2, a 3D laser scanner that scans a pulse laser to measure a distance to a measurement object in a measurement range and calculates three-dimensional data based on at least the distance measurement result has at least 2 measurement ranges. The image is divided into the above sections, each partial image is captured to acquire a partial image, and the partial images are combined to create a panoramic image of the measurement range. At this time, of the partial images to be combined, at least the image of the section including the measurement object is taken under the optimum imaging condition. As a result, a high-quality image can be obtained for the measurement object regardless of the position of the measurement object in the panoramic image.

  Patent Document 3 discloses an apparatus in which an image projection apparatus and an imaging apparatus are integrated. In this apparatus, in a configuration in which a laser beam emitted from a semiconductor laser is scanned to project an image, the distance to the object is measured using the projection light, the focal position is adjusted, and the object is photographed. I have to.

  Patent Document 4 discloses a system that can perform photographing with a small projector. When the system is used as a projector, light from a light source (for example, a laser light emitting element) is scanned in a two-dimensional direction by a horizontal scanning mirror and a vertical scanning mirror, and a two-dimensional micromirror array (for example, DMD; digital micromirror device). ). In the micromirror array, the angle of the mirror corresponding to each pixel is switched according to the projection image, and only the light reflected by the predetermined mirror is irradiated onto the screen via the projection optical system. On the other hand, when the system is used as an imaging apparatus, the projection optical system is used as an imaging optical system. That is, light from a subject incident through the projection optical system enters the micromirror array. At this time, all the mirrors of the micromirror array are controlled so as to be directed in the same direction (at the same angle), and work as one mirror as a whole. The light reflected by the micromirror array is received by the two-dimensional imaging device.

JP 2014-219330 A (refer to claim 1, paragraphs [0009], [0018], etc.) JP 2012-185053 A (refer to claim 5, paragraph [0019], FIG. 4 etc.) JP 2010-085472 A (refer to claim 1, paragraphs [0021], [0043], [0044], FIG. 1, FIG. 7, etc.) JP 2003-186112 A (refer to claims 4, 10, paragraphs [0065] to [0067], [0073], FIG. 14)

  By the way, in recent years, the use of a monitoring system that can monitor the intrusion of a suspicious person or a suspicious object into a building or a public facility (hereinafter also simply referred to as a building) day or night is increasing. Conventionally, intrusion monitoring of a suspicious person into a building has been mostly based on short-distance shooting. For monitoring within a short distance of several meters to 20 meters inside or outside of a building, that is, monitoring where illumination light reaches, for example, a camera that uses light from a halogen lamp or LED (light emitting diode) as illumination light, or pyroelectric Thermal sensors such as sensors have been used. Since these cameras and thermal sensors have been mass-produced and become inexpensive, there is an advantage that a monitoring system can be constructed at a low cost.

  On the other hand, recently, there has been a problem that UAVs (Unmanned Aerial Vehicles) and unmanned airplanes called drones invade into the premises of buildings. Since these unmanned airplanes are as small as 30 cm to 1 m square and the flight speed is as fast as about 50 km / h, conventional short-distance monitoring cameras and thermal sensors can be used to capture unmanned airplanes. Is difficult. For this reason, it is necessary to monitor a distant place away from the building by a distance of about 100 m to 300 m with a camera installed near the building and detect an unmanned airplane flying in the distance. At the same time, it is necessary to be able to monitor a suspicious person who tries to enter a building with the camera.

  However, for example, when monitoring the presence of suspicious objects such as distant suspicious people away from the building at a distance of about 100 m to 300 m or unmanned airplanes at night, inexpensive lights such as halogen lamps and LEDs are sufficient. Absent.

  In this regard, sensors that can detect the temperature of the object itself, such as mid-infrared or far-infrared sensors, are suitable for remote monitoring at night because they do not require lighting (because they can detect objects by temperature without lighting). . Recently, as an infrared sensor, a microbolometer and a thermopile, which are non-cooling sensors, have been sold at low cost. However, these mid-infrared or far-infrared sensors have only tens to hundreds of thousands of pixels. This is because the sensor manufacturing technology is not developed and the wavelength range from the mid-infrared to the far-infrared is as long as 3 to 14 μm, so that the resolution does not decrease due to the diffraction effect, so one pixel size is 10 μm or less. Related to things that cannot be done.

  Even if the manufacturing technology is improved and it becomes possible to manufacture a mid-infrared or far-infrared sensor with a large number of pixels, the size of the sensor becomes enormous. Special things are required. As a result, the lens is quite expensive. For this reason, a system using a mid-infrared or far-infrared sensor is not realistic in remote monitoring. In addition, since the image captured by the mid-infrared or far-infrared sensor is temperature information, it is difficult to determine the shape of the captured object from the image, and the suspicious person or suspicious object based on the image is identified. Becomes difficult.

  Considering the above, it is desired to realize a monitoring system using a small sensor that is inexpensive and has a large number of pixels in remote monitoring.

  In addition, a powerful light source is required to illuminate distant objects. As a powerful light source, for example, when a light source that emits visible light is considered, a halogen lamp used for a searchlight can be used. However, if the searchlight is always turned on during nighttime monitoring, power consumption increases. Furthermore, if the illumination optical system and the photographing optical system are configured completely separately, the entire system may be increased in size. In addition, for example, in nighttime monitoring, it is necessary to perform illumination and photographing at the same time (because the surroundings are dark, it is necessary to photograph in an illuminated state).

  Therefore, in a system for monitoring a distant place, it is desired to appropriately select a light source used for illumination and to realize a system capable of simultaneously performing illumination and photographing with a small configuration.

  In addition, it is thought that it is difficult to apply the structure of the patent documents 1-4 mentioned above to the system which monitors a distant place in the following points. In Patent Document 1, since the light projecting system and the light receiving system are arranged at a distance of several tens of kilometers, when the configuration of Patent Document 1 is applied to a monitoring system, the entire system becomes large. In addition, it is assumed that a light emitting system or a light receiving system is installed outside the building premises (because the distance between each other is a long distance). is not. In Patent Document 2, since a partial image is acquired by shooting for each section into which the measurement range is divided, the shooting timing is different for each section. Therefore, for example, even when an object moving at a high speed of 50 km / h is monitored, the object cannot be detected if the timing at which the object enters the desired section does not match the timing at which the section is photographed. There is a high possibility of missing an object. In Patent Document 3, the image projection device and the imaging device are realized by the same device, but the projection optical system and the imaging optical system are configured separately, and there is a concern about an increase in the size of the system. In Patent Document 4, the projection optical system is also used as a photographing optical system. However, since the operation of the micromirror device is different between the projection and the photographing, the projection and the photographing cannot be performed at the same time. Nighttime monitoring that requires simultaneous shooting is not possible.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to monitor a distant place by using a small sensor with a small number of pixels and a light source suitable for illumination. Thus, it is an object of the present invention to provide a monitoring system capable of monitoring a distant place even at night by performing illumination and photographing at the same time.

  A monitoring system according to one aspect of the present invention has a sensitivity to at least one wavelength region of visible light and near-infrared light, and a wide-angle photographing lens whose diagonal half field angle ω is 30 ° or more and whose image side is almost telecentric. An imaging sensor that captures an imaging object at a distance of 100 m or more and 300 m or less via the wide-angle imaging lens, and a laser beam having an intensity peak in the wavelength region where the imaging sensor is sensitive. A laser light source that emits, and an illumination optical system that guides the laser light emitted from the laser light source to the imaging target side, and the wide-angle imaging lens also serves as a part of the illumination optical system, The illumination optical system scans the laser light emitted from the laser light source and incident on the wide-angle photographing lens, so that the imaging sensor photographs through the wide-angle photographing lens. And a laser beam scanning mechanism that sequentially shifts the illumination position of the laser beam that illuminates a part of the imaging range via the wide-angle imaging lens within the imaging range of the imaging target.

  An imaging sensor having sensitivity in the visible or near-infrared wavelength region is less expensive than the mid-infrared or far-infrared sensor, and is small even if the number of pixels is large because the size of one pixel is small. Further, the illumination of the imaging target is performed using a laser light source. The laser light source emits laser light having an intensity peak in the visible or near infrared wavelength region. At this time, since the laser light source can produce a parallel light beam having a uniform phase and wavelength as laser light, it is possible to illuminate a distant object to be photographed by irradiating a distant object of approximately 500 m with a laser light of approximately 1000 W. it can. Therefore, by using the laser light source, it is possible to illuminate a subject to be photographed separated by a distance of 100 m or more and 300 m or less with lower power consumption than when using a searchlight. In addition, the subject to be photographed by the imaging sensor is photographed through a wide-angle photographing lens, but the wide-angle photographing lens has a diagonal half angle of view ω of 30 ° or more, so that a wide range can be photographed at a time. .

  In addition, since the wide-angle photographing lens is almost telecentric on the image side, it is possible to easily realize a configuration in which the wide-angle photographing lens also serves as a part of the illumination optical system. That is, if the wide-angle shooting lens is image-side telecentric, a sufficient lens back can be secured. Therefore, for example, an optical path combining member is disposed between the wide-angle shooting lens and the image sensor, and the optical path of the illumination optical system (laser light) And the optical path of the imaging optical system (the optical path of light incident on the imaging sensor from the imaging target side via the wide-angle imaging lens) and the laser beam is guided to the imaging target side via the wide-angle imaging lens. It becomes possible. As described above, the wide-angle photographing lens also serves as a part of the illumination optical system, whereby the system configuration is simplified and the system can be downsized. Further, since the wide-angle photographing lens also serves as a part of the illumination optical system, it is possible to simultaneously photograph the photographing object through the wide-angle photographing lens while illuminating the photographing object with the laser light through the wide-angle photographing lens. Thereby, it is possible to monitor the photographing object even at night when illumination is required.

  Further, the laser light has a narrow illumination range, and can illuminate only a part of the range photographed through the wide-angle photographing lens. However, the laser beam scanning mechanism scans the laser beam and sequentially shifts the illumination position of the laser beam, so that the image sensor adds the images taken at each illumination position by one frame and adds one image. A bright wide-angle shot image can be obtained. Therefore, even in a configuration in which laser light with a narrow illumination range is used for illumination, a wide-angle captured image can be obtained and a distant place can be monitored. In other words, even in a configuration using a small-sized imaging sensor that receives visible light and near-infrared light and that is inexpensive and has a large number of pixels, and a laser light source that emits laser light with a narrow illumination range, remote monitoring is performed. be able to.

  The illumination optical system includes an optical path combining member that combines an optical path of the laser light emitted from the laser light scanning mechanism with an optical path of light incident on the imaging sensor from the imaging target side through the wide-angle imaging lens. In addition, the laser beam may be incident on the wide-angle photographing lens via the optical path combining member.

  Laser light emitted from the laser light scanning mechanism is guided to the photographing target side through the optical path combining member and the wide-angle photographing lens to illuminate the photographing target. In this case, the wide-angle photographing lens constitutes a photographing optical system that guides light from the photographing target side to the image sensor, and also serves as a part of the illumination optical system. That is, by using the optical path combining member, it is possible to reliably realize a configuration in which the wide-angle photographing lens also serves as a part of the illumination optical system.

  The laser beam scanning mechanism may include a first parallel plate disposed on the light emission side of the laser light source and a plate rotation mechanism that rotates the first parallel plate.

  By rotating the first parallel plate by the plate rotation mechanism, the refraction angle of the laser beam inside the first parallel plate is changed, and the emission position of the laser beam from the first parallel plate is changed. Can be shifted. Thereby, a laser beam can be scanned.

  The laser beam scanning mechanism includes a second parallel plate that is positioned so that the laser beam from the laser light source is vertically incident, and a slide mechanism that slides the second parallel plate in a direction perpendicular to the thickness direction. The laser light incident surface and the light exit surface are diffractive surfaces, respectively, and the diffraction characteristics of the diffractive surfaces are In the sliding direction perpendicular to the thickness direction of the two parallel plates, the diffraction angle continuously changes depending on the incident position of the laser beam, and the laser beam incident perpendicularly to the incident surface is perpendicular to the emission surface. It may be set to be emitted.

  Since the second parallel plate has a characteristic that the diffraction angle varies depending on the incident position of the laser beam, the second parallel plate is slid vertically by the slide mechanism so as to be perpendicular to the incident surface of the second parallel plate. The laser beam incident and emitted perpendicularly from the exit surface can be shifted in the sliding direction in accordance with the sliding amount of the second parallel plate, whereby the laser beam can be scanned.

  The laser beam scanning mechanism includes an acoustooptic device and a first drive circuit that applies ultrasonic waves to the crystal of the acoustooptic device, and the first drive circuit includes the crystal of the acoustooptic device. The laser beam may be emitted by changing the diffraction angle of the laser beam incident on the acoustooptic device by changing the frequency of the ultrasonic wave applied to the acoustooptic device.

  By changing the diffraction angle of the laser beam in the acoustooptic device, the emission position of the laser beam from the acoustooptic device can be shifted. Thereby, a laser beam can be scanned.

  The laser beam scanning mechanism includes a plane mirror, a rotary paraboloid mirror, and a mirror rotation mechanism that rotates the plane mirror, and the rotation center of the plane mirror is the rotation paraboloid. At the focal position of the mirror, the plane mirror reflects the laser light from the laser light source at the rotation center and guides it to the rotating paraboloid mirror, and the mirror rotation mechanism includes the plane mirror The incident position of the laser beam incident on the rotary paraboloid mirror may be changed by rotating the lens.

  By rotating the plane mirror by the mirror rotation mechanism, the position of the laser beam reflected by the plane mirror entering the rotary paraboloid mirror is changed. At this time, since the center of rotation of the plane mirror is at the focal position of the rotary paraboloid mirror, the plane mirror is reflected by the plane mirror at each position of the rotary paraboloid mirror regardless of the rotation position of the plane mirror. The incident laser light is reflected there and emitted in the same direction (parallel to each other). That is, in this case, the height of the laser light reflected by the rotary paraboloid mirror (the distance from the optical path of the laser light before entering the flat mirror) changes according to the rotation position of the flat mirror. Thereby, a laser beam can be scanned in the said height direction.

  The laser beam scanning mechanism includes an acoustooptic element, a rotating paraboloid mirror, and a second drive circuit that applies ultrasonic waves to the crystal of the acoustooptic element, and a part of the acoustooptic element includes The acoustooptic device diffracts and reflects the laser light from the laser light source at the part and guides it to the rotary paraboloid mirror; The drive circuit changes the diffraction angle of the laser beam by changing the frequency of the ultrasonic wave applied to the crystal of the acoustooptic device, and enters the rotating paraboloidal mirror. The position may be changed.

  By changing the frequency of the ultrasonic wave applied to the crystal of the acoustooptic device by the second drive circuit, the diffraction angle of the laser beam diffracted and reflected by the acoustooptic device is changed, whereby the diffracted and reflected laser beam is changed. The position of incidence on the paraboloidal mirror changes. At this time, a part of the acousto-optic element that diffracts and reflects the laser light is at the focal position of the rotary paraboloid mirror, and is reflected by the above-mentioned part of the acousto-optic element and enters each position of the rotary paraboloid mirror. The laser light thus reflected is reflected and emitted in the same direction (in a direction parallel to each other). That is, in this case, the height of the laser beam reflected by the rotary paraboloid mirror according to the frequency of the ultrasonic wave applied to the acoustooptic device (the distance from the optical path of the laser beam before entering the plane mirror). Changes. Thereby, a laser beam can be scanned in the said height direction.

  The laser beam scanning mechanism preferably scans the laser beam in two directions perpendicular to each other within a plane perpendicular to the optical axis of the wide-angle imaging lens. In this case, since the illumination position of the laser light is shifted in the two directions (for example, the horizontal direction and the vertical direction) to illuminate the object, a bright captured image can be obtained in the horizontal direction and the vertical direction over the entire frame.

  The monitoring system may further include an image recognition unit that recognizes a suspicious person or a suspicious object by performing an image recognition process on image data of an image captured and acquired by the imaging sensor.

  By performing image recognition processing by the image recognition unit, it is possible to recognize a suspicious person or a suspicious object in distinction from harmless objects such as animals, plants, and garbage. Thereby, it is possible to realize a system for performing advanced monitoring.

  The monitoring system is configured to cause the laser light source to emit light in a pulsed manner, and to drive a shutter of the imaging sensor in synchronization with the pulsed light emission, and the laser light output by the pulsed light emission is an object to be imaged. A distance measuring unit that measures a time until it is reflected and incident on the imaging sensor, and measures a distance to the object, and the image recognition unit includes the result of the image recognition process, and It is desirable to determine whether or not there is a suspicious person or a suspicious object based on the distance measured by the distance measuring unit.

  For example, even if the image of the photographed object is small or the shape of the object cannot be clearly recognized, if the distance to the object is known, the approximate size of the object can be known, and the shape of the object can also be grasped Is possible. Therefore, the image recognizing unit determines the presence or absence of a suspicious person or a suspicious object based on the result of the image recognition process and the distance to the object measured by the distance measuring unit. It is possible to improve and perform more advanced monitoring.

  The wavelength range of the visible light may be 450 nm or more and 650 nm or less, and the wavelength range of the near infrared light may be 780 nm or more and 1000 nm or less. In the configuration in which the imaging sensor is sensitive to at least one of visible light in the wavelength range and near-infrared light in the wavelength range, and the laser light source emits laser light having an intensity peak in at least one of the wavelength ranges. The effect of can be obtained.

  By scanning the laser beam with the laser beam scanning mechanism and sequentially shifting the illumination position of the laser beam, the imaging sensor adds up the images captured at each illumination position by one frame and captures one bright wide-angle image. An image can be obtained. Thereby, even in a configuration using a sensor that receives visible light and near-infrared light, that is, a small-sized imaging sensor that is inexpensive and has a large number of pixels, and a laser light source that emits laser light with a narrow illumination range, You can monitor far away. In addition, since the wide-angle photographing lens also serves as a part of the illumination optical system, it is possible to realize a compact system and to monitor far away at night by performing illumination and photographing at the same time.

It is explanatory drawing which shows the structure of the principal part of the monitoring system which concerns on one Embodiment of this invention. It is explanatory drawing which shows the other structure of the said monitoring system. It is explanatory drawing which shows the structure of the laser beam scanning mechanism applied to the monitoring system in other embodiment of this invention. It is explanatory drawing which shows typically the diffraction characteristic of each surface of the parallel plate of the said laser beam scanning mechanism. It is explanatory drawing which shows the other structure of the said laser beam scanning mechanism. It is explanatory drawing which shows the structure of the laser beam scanning mechanism applied to the monitoring system which concerns on further another embodiment of this invention. It is explanatory drawing which shows the other structure of the said laser beam scanning mechanism. It is a block diagram which shows the structure of the principal part of the monitoring system which concerns on further another embodiment of this invention. It is a flowchart which shows the flow of operation | movement in the said monitoring system.

  An embodiment of the present invention will be described below with reference to the drawings. In the present specification, when the numerical range is expressed as A to B, the numerical value range includes the values of the lower limit A and the upper limit B.

[Terminology]
First, definitions of main terms used in the present specification are shown below.
Far-infrared (light): Refers mainly to radiation in the wavelength range of 7 μm to 14 μm. Incidentally, the body temperature of humans and animals is radiated light having a wavelength of 8 μm or more and 12 μm or less.
Mid-infrared (light): Refers mainly to radiation in the wavelength range of 2.5 μm or more and less than 7 μm.
Near-infrared (light): Refers mainly to radiated light having a wavelength in the range of 700 nm to less than 2500 nm, and particularly refers to radiated light having a wavelength in the range of 780 nm to 1000 nm.
Visible (light): Refers mainly to the emitted light in the wavelength range of 400 nm to less than 700 nm, and particularly refers to the emitted light in the wavelength range of 450 nm to 650 nm.
Object detection: The presence of an object is detected from sound and images.
Object recognition: Judge what an existing object is from sound and images.
Surveillance: A state in which attention is paid to whether there are suspicious persons or suspicious objects inside or outside the guarded area.
Image recognition: Refers to finding an image that matches a predetermined feature from an image.
Telecentric: A state where the central ray passing through the center of the pupil of the lens system is parallel to the optical axis both on and off axis. When the central ray is all parallel to the optical axis on the image forming side or the reduction side, it is particularly called image side telecentric. The light beam passing through the periphery of the pupil is not necessarily parallel to the optical axis, and is different from the parallel light flux.

[Embodiment 1]
FIG. 1 is an explanatory diagram showing a configuration of a main part of the monitoring system 1 of the present embodiment. The monitoring system 1 includes a laser light source 2, an illumination optical system 3, and an image sensor 4.

  The laser light source 2 is a light source that emits laser light having an intensity peak in a near-infrared wavelength region (for example, near a wavelength of 900 nm), for example. The laser light source 2 may be composed of any light source as long as it emits laser light having an intensity peak in a wavelength range in which the image sensor 4 has sensitivity (emits laser light of any wavelength. May be). Therefore, when the imaging sensor 4 has sensitivity in the visible light wavelength region, the laser light source 2 may be configured by a light source that emits laser light having an intensity peak in the visible light wavelength region. Further, when the imaging sensor 4 has sensitivity in both visible light and near-infrared wavelength regions, the laser light source 2 includes a light source that emits laser light having an intensity peak in the visible light wavelength region, What is necessary is just to comprise in combination with the light source which radiate | emits the laser beam which has an intensity peak in an infrared wavelength range. The laser light source 2 emits a substantially parallel light beam with an output of about 1000 W.

  The imaging sensor 4 has sensitivity in at least one wavelength region of visible light and near-infrared light, and captures an imaging target separated by a distance of 100 m or more and 300 m or less via a wide-angle imaging lens 11 described later.

  Note that the imaging target of the imaging sensor 4 includes tangible objects such as objects, and intangible objects such as spaces, and the objects include suspicious objects such as unmanned airplanes and suspicious persons. Here, in order to facilitate understanding of the description, the imaging target is described as an object (for example, an unmanned airplane). When the object does not exist in the air (when there is no suspicious object), the object to be imaged is a space in a certain range at a position away from the image sensor 4 by the distance, and the image sensor 4 Is taken as a subject to be photographed. From the above, it is assumed that “object” appearing below can be appropriately read as “photographing object”.

  The imaging sensor 4 is, for example, a 1/6 inch diagonal sensor having 2.5 million pixels, and has sensitivity in the visible to near-infrared wavelength region. As such an image sensor 4, a general image sensor such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) can be used. The imaging sensor 4 captures an object separated by 100 m or more and 300 m or less via the wide-angle imaging lens 11 in accordance with a driving frequency of 30 Hz or 60 Hz in a laser beam scanning mechanism 4 described later. For example, a 30 cm square object 200 m away is photographed by the image sensor 4 in an area of 1.5 pixels × 1.5 pixels. Note that the size of one pixel in the image sensor 4 is, for example, 3 μm × 3 μm.

  The illumination optical system 3 is an optical system that guides laser light emitted from the laser light source 2 to the object side, and includes a wide-angle photographing lens 11, an optical path synthesis prism 12, a concave lens 13, and a laser light scanning mechanism 14. doing.

  The wide-angle photographic lens 11 is a lens system in which the diagonal half field angle ω is 30 ° or more and the image side is almost telecentric. In the present embodiment, for example, the horizontal total angle of view (the total angle of view in the direction parallel to the paper surface of FIG. 1) of the wide-angle photographing lens 11 is 90 °, and the vertical total angle of view (the direction perpendicular to the paper surface of FIG. 1). The total angle of view) is 60 °, and the diagonal half angle of view ω is 50.5 °. The wide-angle photographing lens 11 is a photographing optical system that guides object light to the imaging sensor 4, but constitutes a part of the illumination optical system 3. The number of lenses constituting the wide-angle photographic lens 11 may be one or plural.

  The optical path synthesis prism 12 is an optical path synthesis member that synthesizes the optical path of the laser light emitted from the laser light scanning mechanism 14 with the optical path of the object light incident on the image sensor 4 from the wide angle photographing lens 11. The optical path combining prism 12 is formed, for example, by joining slopes of two prisms whose cross sections are right-angled isosceles triangles via an optical thin film that functions as a half mirror. By arranging the optical path combining prism 12 in the optical path between the wide-angle photographing lens 11 and the image sensor 4, the laser light is incident from the direction perpendicular to the optical axis of the wide-angle photographing lens 11, and the laser light. Can be incident on the wide-angle photographing lens 11 through the optical path combining member 12.

  The concave lens 13 is a light beam width expanding element that expands the light beam width of the laser light emitted from the laser light scanning mechanism 14 and guides it to the optical path combining prism 12, and is constituted by an aspherical concave lens, for example. The concave lens 13 adjusts (enlarges) the light flux width so that the area of the illumination light flux by the laser light becomes about 1/100 of the area of the entire photographing range photographed by the image sensor 4 when the photographing distance is 200 m, for example. ) Is provided. By expanding the beam width of the laser beam, the intensity of the laser beam per unit area decreases, so if the laser beam is incident on the human eye by any chance, the influence (for example, risk of blindness) is reduced. can do. Instead of providing the concave lens 13, a convex lens may be provided as a relay lens so as to increase the beam width of the laser light.

  The laser beam scanning mechanism 14 scans the laser beam emitted from the laser light source 2 and incident on the wide-angle imaging lens 11, so that it is within the imaging range of the imaging target being imaged by the imaging sensor 4 via the wide-angle imaging lens 11. Thus, the illumination position of the laser beam that illuminates a part of the imaging range via the wide-angle imaging lens 11 is sequentially shifted. More specifically, the laser beam scanning mechanism 14 includes a parallel plate 21 (first parallel plate) and a plate rotation mechanism 22.

  The parallel plate 21 is a transparent substrate in which two surfaces 21 a and 21 b facing each other are positioned in parallel, and is disposed on the light emission side of the laser light source 2. The flat plate rotating mechanism 22 is a mechanism for rotating the parallel flat plate 21 in the horizontal direction and the vertical direction, and rotates the parallel flat plate 21 at a driving frequency of 30 Hz or 60 Hz. Such a flat plate rotation mechanism 22 can be constituted by an actuator that can be driven electrically at high speed, such as a piezoelectric element. Although FIG. 1 shows a momentary rotation state of the parallel plate 21, the parallel plate 21 is driven by the plate rotation mechanism 22 so as to constantly rotate. The horizontal direction and the vertical direction of the parallel plate 21 correspond to the horizontal direction and the vertical direction of the object to be monitored, that is, two directions perpendicular to each other in the plane perpendicular to the optical axis of the wide-angle photographing lens 11. (In the following description, the horizontal direction and the vertical direction in the laser beam scanning mechanism 14 correspond to two directions perpendicular to each other in a plane perpendicular to the optical axis of the wide-angle imaging lens 11, respectively). To do).

  In the above configuration, the laser light emitted from the laser light source 2 is transmitted through the parallel plate 21, the light flux width is enlarged by the concave lens 13, and reflected by the optical path synthesis prism 12 in the direction of the wide-angle photographing lens 11. The laser light is emitted to the object side through the wide-angle photographing lens 11 and illuminates a part of the object. The illumination light reflected by the object follows an optical path opposite to that described above, enters the wide-angle photographing lens 11, passes through the optical path combining prism 12, and enters the imaging sensor 4.

  Here, if the parallel plate 21 is inclined with respect to the optical path of the incident laser light, the laser light is refracted by the surface 21 a in the direction in which the parallel plate 21 is inclined when passing through the parallel plate 21. The light is refracted to the original angle again by the surface 21b (in an optical path parallel to the optical path before entering the surface 21a) and emitted. That is, the laser beam moves in parallel by an amount corresponding to the thickness of the parallel plate 21 when passing through the parallel plate 21. In addition, by changing the inclination of the parallel plate 21, the incident angle of the laser beam with respect to the parallel plate 21 changes and the refraction angle also changes. For this reason, the laser light emitted from the parallel plate 21 can be translated by an amount corresponding to the rotation angle of the parallel plate 21 by the rotation of the parallel plate 21.

  For example, in the case where a transparent substrate having a thickness of 34 mm and a refractive index of 1.51 with respect to a wavelength of 900 nm is used as the parallel plate 21, it is inclined by ± 13 ° in the horizontal direction and ± 7.35 ° in the vertical direction. By rotating the parallel plate 21, the laser beam is moved in parallel by ± 2.6 mm in the horizontal direction and ± 1.47 mm in the vertical direction. When the parallel plate 21 is thin (for example, a plate having a thickness of 25 mm), the parallel plate 21 is rotated so that it is inclined ± 17.5 ° in the horizontal direction and ± 10 ° in the vertical direction. As a result, a parallel movement of the laser light of ± 2.6 mm in the horizontal direction and ± 1.47 mm in the vertical direction occurs.

  In the present embodiment, as described above, the wide-angle photographic lens 11 is an optical system that is almost telecentric on the image side. Therefore, when the laser light is translated on the image side, the angle of the illumination light (laser light) changes on the object side. To do. Therefore, by rotating the parallel plate 21 by the plate rotation mechanism 22 and moving the laser beam emitted from the parallel plate 21 in parallel, the laser beam applied to the object can be scanned. That is, the illumination position of the laser beam that illuminates a part of the above range can be sequentially shifted within the range imaged by the imaging sensor 4 of 1/6 inch diagonal.

  The laser light has a narrow illumination range (even if the light beam width is increased by the concave lens 13), and can illuminate only a part of the range photographed at a wide angle via the wide angle photographing lens 11. However, by scanning the laser beam as described above and sequentially shifting the illumination position, the imaging sensor 4 adds up one frame of the images captured at each illumination position to form one bright wide-angle captured image. Can be obtained. In other words, the laser beam is scanned within the time required to shoot for one frame, and each illumination position is sequentially shifted. On the other hand, the imaging sensor 4 corresponds to the amount of light received from the object (the reflected light of the illumination light). Charge is accumulated in each pixel, and when the scanning of the laser beam for one frame is completed, the accumulated charge is read from each pixel, so that a bright photographed image can be obtained over the entire range being photographed. it can.

  A sensor that receives visible light or near-infrared light is less expensive than a sensor that receives mid-infrared light or far-infrared light, and is small even if the number of pixels is large. Therefore, even a configuration using such a low-priced, large-number image pickup sensor 4 and a laser light source 2 that emits laser light with a narrow illumination range is used to photograph and monitor distant objects. be able to. Further, since the wide-angle photographing lens 11 also serves as a part of the illumination optical system 3, a small monitoring system 1 can be realized, and the illumination by the laser light and the photographing by the image sensor 4 are performed as described above. You can go at the same time and monitor the presence of distant objects even at night.

  In addition, since it becomes dark while the object is not illuminated by the laser light, it is not necessary to limit the readout time with the shutter in the image sensor 4. In addition, when accumulating charges for one frame, it is only necessary to open the shutter for one frame. Therefore, unlike laser radar, the scanning timing of the laser beam and the shutter of the image sensor 4 are synchronized. Is also unnecessary.

  In this embodiment, an optical path synthesis prism 12 is placed in the optical path between the imaging optical system (wide-angle imaging lens 11) and the image sensor 4, and illumination laser light is transmitted via the optical path synthesis prism 12. The light is incident on the wide-angle photographing lens 11 and the object is illuminated through the wide-angle photographing lens 11. In this way, by using the optical path combining prism 12, it is possible to reliably realize a configuration in which the wide-angle photographing lens 11 also serves as a part of the illumination optical system 3 that illuminates an object.

  The laser beam scanning mechanism 14 includes a parallel plate 21 and a plate rotation mechanism 22. By rotating the parallel plate 21 by the plate rotation mechanism 22, the laser beam incident on the parallel plate 21 can be scanned as described above.

  Further, when illuminating an object using laser light with a narrow illumination range, scanning with laser light is necessary as described above. A laser with a strong output that can illuminate a distant place is emitted from a laser light source as almost parallel light and has a narrow beam width. Therefore, an optical element such as a mirror that deflects and scans the laser light is placed near the laser light source. If the laser beam is deflected by a mirror and the object is directly illuminated by the laser beam, a compact scanning mechanism can be realized.

  However, when illuminating far away with the scanning mechanism using a mirror, the mirror must be reciprocated many times in order to illuminate the entire imaging range with a small beam width. In addition, since a strong light beam may be applied to the human eye and be damaged, it is necessary to consider increasing the beam width of the laser beam appropriately. At this time, if an optical system for widening the beam width is installed on the object side of the scanning mechanism, the optical system becomes large. In addition, since the point light source is irradiated in a planar shape, it is necessary to use an optical system different from the photographing optical system. Conversely, if an optical system that widens the beam width is placed near the laser light source and a scanning mirror is placed on the object side of the optical system, the optical system can be made somewhat small, but the beam width is widened. Therefore, the mirror for scanning with the laser beam becomes large.

  In this regard, in the present embodiment, an optical path synthesis prism 12 is disposed in the optical path between the wide-angle imaging lens 11 and the image sensor 4, and the laser beam scanning mechanism 14 is provided on the laser light source 2 side with respect to the optical path synthesis prism 12. Since the laser beam is scanned by rotation of the parallel plate 21, the entire parallel imaging area of the image sensor 4 is used even when the parallel plate 21 is small and the rotation angle of the parallel plate 21 is small. Thus, the illumination position of the laser beam can be shifted and illuminated. Further, since the rotation angle of the parallel plate 21 is small, an optical system (concave lens 13 in this embodiment) for widening the beam width of the laser light is arranged on the light emission side of the parallel plate 21 as in this embodiment. Even in the arrangement, it is possible to avoid an increase in the size of the concave lens 13. Further, by arranging the concave lens 13 on the light emitting side of the parallel plate 21, it is possible to arrange the parallel plate 21 and the laser light source 2 close to each other. Therefore, in the configuration using the optical path combining prism 12 and the laser beam scanning mechanism 14, the entire apparatus is compared with the configuration in which the laser beam is scanned with the mirror and the object is illuminated without performing the optical path combining between the illumination system and the imaging system. It is very easy to reduce the size.

  Further, the laser beam scanning mechanism 14 scans the laser beam applied to the object in two directions (horizontal direction and vertical direction) perpendicular to each other in a plane perpendicular to the optical axis of the wide-angle imaging lens 11, and thus the imaging sensor 4. Even when a wide-angle photographed image is obtained, laser light with a narrow illumination range can be scanned in the horizontal and vertical directions, and a bright photographed image in the horizontal and vertical directions can be obtained for the entire frame.

  Incidentally, FIG. 2 shows another configuration of the monitoring system 1 of the present embodiment. Instead of the optical path combining prism 12 described above, a parallel plate type optical path combining element 12 '(optical path combining member) may be disposed. The optical path combining element 12 'is configured by forming a reflective film 12a functioning as a half mirror on one surface side of a transparent parallel plate 12b. Each member is configured such that light transmitted through the parallel plate 12b of the optical path combining element 12 ′ becomes illumination light (laser light), and light reflected by the reflective film 12a becomes object light directed from the object side toward the image sensor 4. Is arranged. As described above, even when the optical path combining element 12 ′ is used, it is possible to realize a compact configuration by combining the optical paths between the illumination system and the imaging system.

  The light transmitted through the parallel plate 12b of the optical path combining element 12 ′ is used as illumination light. If the parallel plate 12b is inserted obliquely into the optical path, an aberration (for example, astigmatism) occurs, and the parallel plate 12b. This is because the image performance is deteriorated due to the above-mentioned aberration when the light that passes through is taken as imaging light.

[Embodiment 2]
FIG. 3 is an explanatory diagram showing a configuration of a laser beam scanning mechanism 14 applied to the monitoring system 1 according to another embodiment of the present invention. The laser beam scanning mechanism 14 may include a parallel plate 23 (second parallel plate) and a drive mechanism 24. In the monitoring system 1, the configuration other than the laser beam scanning mechanism 14 is the same as that of the first embodiment shown in FIG.

  The drive mechanism 24 has a slide mechanism 24a and a rotation mechanism 24b. The slide mechanism 24a is a mechanism that slides the parallel plate 23 in a direction perpendicular to the thickness direction (for example, a direction corresponding to the horizontal direction of the object), and is configured by a general slide mechanism including, for example, a cam, a shaft, and a motor. ing. The rotation mechanism 24b is a mechanism that rotates the parallel plate 23 with the axis along the slide direction of the parallel plate 23 as a rotation axis, and is configured by an actuator such as a piezo element, for example. Therefore, the parallel plate 23 can be rotated by the rotation mechanism 24b in a direction corresponding to the vertical direction of the object, for example. Even if the slide mechanism 24a slides the parallel plate 23 in the direction corresponding to the vertical direction of the object, and the rotation mechanism 24b rotates the parallel plate 23 in the direction corresponding to the horizontal direction of the object. Good.

  The parallel plate 23 has surfaces 23a and 23b facing each other, and is positioned so that the laser light from the laser light source 2 is incident vertically. The surface 23a of the parallel plate 23 is an incident surface for the laser beam, and the surface 23b is an exit surface for the incident laser beam. The surfaces 23a and 23b are diffractive surfaces, respectively. These diffractive surfaces can be realized, for example, by forming a diffraction grating (blazed type, comb blade type, etc.) on the surfaces 23a and 23b, or by arranging a hologram optical element. Here, the surfaces 23a and 23b are formed of linear diffraction gratings.

  FIG. 4 schematically shows the diffraction characteristics of the surfaces 23 a and 23 b of the parallel plate 23. As shown in the figure, the diffraction characteristics of the surfaces 23a and 23b are such that the diffraction angle continuously changes depending on the incident position of the laser beam in the sliding direction perpendicular to the thickness direction of the parallel plate 23, and is perpendicular to the surface 23a. The incident laser beam is set so as to be emitted vertically from the surface 23b. In the present embodiment, as shown in FIG. 4, the diffraction characteristics of the surfaces 23a and 23b are symmetric in the sliding direction with respect to the central portion in the sliding direction, but may be asymmetrical.

  In this configuration, the laser light emitted from the laser light source 2 is perpendicularly incident on the surface 23a of the parallel plate 23, is diffracted by the surface 23a, is further diffracted by the surface 23b, and is perpendicular to the surface 23b. Emitted in the direction. At this time, the surfaces 23 and 23b have diffraction characteristics in which the diffraction angle changes continuously (in a stepless manner) depending on the incident position of the laser beam, so by sliding the parallel plate 23 in the sliding direction, As shown in FIG. 3, the emission position of the laser beam can be shifted in the sliding direction (for example, the horizontal direction). In addition, due to the diffraction characteristics of the parallel plate 23, the shift amount of the laser light in the slide direction can be continuously changed according to the slide amount of the parallel plate 23. Therefore, the laser beam can be continuously shifted in the sliding direction by continuously sliding the parallel plate 23. As a result, even with the configuration of FIG. 3, the laser beam can be scanned (in the sliding direction).

  Since the diffraction grating can only scan in one dimension (one direction), scanning in the other direction is performed by rotating the parallel plate 23 in the vertical direction by the rotating mechanism 24b. That is, laser light is scanned in one direction by sliding the parallel plate 23 by the slide mechanism 24a, and laser light is scanned in the other direction by rotation of the parallel plate 23 by the rotation mechanism 24b. The laser beam can be scanned in two directions (horizontal direction and vertical direction) perpendicular to each other in a plane perpendicular to the optical axis.

  At this time, for example, when the imaging sensor 4 has a horizontally long (horizontal length> vertical length) imaging region, that is, when the captured image is horizontally long, the vertical rotation angle is (in the horizontal direction). Since the angle may be small (compared to the case of rotation), for example, the parallel plate 23 having a thickness of 25 mm is tilted by ± 10 ° in the vertical direction, thereby the vertical direction of the imaging sensor 4 having a diagonal size of 1/6 inch. Can be scanned.

  Further, when the imaging region is horizontally long, for example, in the configuration in which the parallel plate is rotated in the horizontal direction and the laser beam is scanned, it is necessary to largely rotate the parallel plate, and the drive mechanism and the laser beam scanning mechanism are There is concern about the increase in size. On the other hand, as shown in FIG. 3, in the horizontal direction, the parallel plate 23 is enlarged in the horizontal direction by using the diffraction effect on the diffraction surface and scanning the laser beam by sliding the parallel plate 23. Since the laser beam can be scanned without being tilted, the drive mechanism 24 for driving the parallel plate 23 and the laser beam scanning mechanism 14 can be further downsized.

  The diffraction grating applied to both surfaces of the parallel plate 23 may be concentric. Even in this case, the diffraction grating may have a cross-section of a blaze type, a comb blade type (step type), or a volume hologram. In this configuration, the slide mechanism 24a is configured so that the parallel plate 23 can slide in two directions (horizontal direction (X direction) and vertical direction (Y direction)) that are perpendicular to each other along the surfaces 23a and 23b. The light can be scanned in two directions perpendicular to each other (directions corresponding to the X direction and the Y direction). Further, it is desirable that the light beam that illuminates the imaging center from the laser light source 2 via the laser beam scanning mechanism 14 and the wide-angle imaging lens 11 passes through the center of the concentric circle.

  Further, the drive mechanism 24 may drive (slide) the parallel plate 23 so that the center of the parallel plate 23 moves linearly along, for example, the X direction, but may slide it in a curved line. For example, when the driving mechanism 24 considers a parabola symmetric with respect to the axis in the Y direction in the plane along the planes 23a and 23b, the driving mechanism 24 is parallel so that the center of the parallel plate 23 moves along the parabola. The flat plate 23 may be driven (slid). The diffraction characteristics along the movement trajectory of the parallel plate 23 at this time are the same as those in FIG.

  When the laser beam scanning mechanism 14 of FIG. 3 is used, the concave lens 13 (see FIG. 1) disposed between the optical path combining prism 12 and the parallel plate 23 has a slight refractive power in the vertical and horizontal directions. It is desirable to use different aspheric lenses. This is to correct the slight divergence of the laser beam in the horizontal direction by the parallel plate 23 having diffraction characteristics.

  By the way, FIG. 5 is explanatory drawing which shows the other structure of the laser beam scanning mechanism 14 of this embodiment. The laser beam scanning mechanism 14 may have a configuration in which an AOD (Acousto-Optic Deflector) 23 ′ that is an acousto-optic element is disposed instead of the parallel plate 23. In this case, the drive mechanism 24 may be configured by the rotation mechanism 24b described above and the drive circuit 24c (first drive circuit). The drive circuit 24c is a drive circuit that applies an ultrasonic wave (signal) to the crystal of the AOD 23 ', and changes the diffraction angle of the laser light incident on the AOD 23' by changing the frequency of the ultrasonic wave applied to the crystal of the AOD 23 '. The laser beam is emitted by changing.

  The AOD acts as a diffraction grating by periodically changing the refractive index by applying ultrasonic vibration to a crystal such as a molten crystal. And the diffraction angle can be freely changed by changing the interval of the diffraction grating according to the vibration frequency of the applied ultrasonic wave. Therefore, the emission position of the laser beam from the AOD 23 ′ can be shifted by changing the diffraction angle of the laser beam by changing the vibration frequency of the ultrasonic wave applied to the AOD 23 ′. Can be scanned. Further, since the ultrasonic vibration is given electrically, a mechanical drive (actuator) is not required unlike the case of using a diffractive element (parallel plate 23) having a groove on the surface of the flat plate. The AOD 23 'also has a fast drive response.

  As shown in FIG. 5, in the configuration using only one AOD 23 ′, the laser beam can be scanned by the AOD 23 ′ in one of the horizontal direction and the vertical direction. It is only necessary to scan the laser beam by a simple rotation. Thereby, the laser beam can be scanned in two directions (horizontal direction and vertical direction) perpendicular to each other.

  In addition, by using two AODs 23 ′ and arranging them at a certain distance, the same function as that of the parallel plate 23 (see FIGS. 3 and 4) having diffraction gratings on both surfaces can be realized. . In this case, since the scanning of the laser beam in each of the horizontal direction and the vertical direction can be performed by the corresponding AOD (one of the two AODs), the drive mechanism 24 is configured only by the drive circuit 24c. (The rotation mechanism 24b can be omitted).

  Further, by providing ultrasonic transducers on the four sides of the AOD 23 ', synchronizing the vibrations, and changing the combination of the strengths of the four ultrasonic transducers, an oblique diffraction element can be realized. Therefore, also in this case, it is possible to realize the scanning of the laser beam in each of the horizontal direction and the vertical direction without using the rotation mechanism.

[Embodiment 3]
FIG. 6 is an explanatory diagram showing a configuration of a laser beam scanning mechanism 14 applied to the monitoring system 1 according to still another embodiment of the present invention. The laser beam scanning mechanism 14 may include a flat mirror 25, a rotary paraboloid mirror 26, a mirror rotation mechanism 27, and a condenser lens 28. In the monitoring system 1, the configuration other than the laser beam scanning mechanism 14 is the same as that of the first embodiment shown in FIG.

  The rotary paraboloid mirror 26 is a mirror having a rotary paraboloid-shaped reflecting surface, and is formed in a size substantially corresponding to a range in which the imaging sensor 4 having a diagonal 1/6 inch size captures an image. The plane mirror 25 reflects the laser light from the laser light source 2 at the rotation center O and guides it to the paraboloid mirror 26. The rotation center O of the plane mirror 25 is at the focal position of the rotary paraboloid mirror 26. The mirror rotation mechanism 27 is a mechanism for rotating the flat mirror 25 in the horizontal direction and the vertical direction, and is configured by an actuator such as a piezoelectric element, for example. The condensing lens 28 is composed of, for example, a convex lens, and is disposed immediately after the laser light source 2, that is, in the optical path between the laser light source 2 and the flat mirror 25, and receives the laser light emitted from the laser light source 2. The light is condensed on the rotation center O of the plane mirror 25.

  In the above configuration, the laser beam emitted from the laser light source 2 and incident on the rotation center O of the plane mirror 25 via the condenser lens 28 is reflected by the rotation center O and then the paraboloid mirror. 26 is incident. By rotating the plane mirror 25 by the mirror rotation mechanism 27, the position of the laser beam reflected by the plane mirror 25 entering the rotary paraboloid mirror 26 is changed. At this time, since the rotation center O of the plane mirror 25 is at the focal position of the rotary paraboloid mirror 26, the plane mirror 25 is reflected by the plane mirror 25 regardless of the rotation position of the plane paraboloid mirror 26. The laser light incident on each position of the mirror 26 is reflected there and emitted in the same direction (parallel to each other).

  That is, in this case, the height of the laser beam reflected by the rotary paraboloid mirror 26 according to the rotational position of the plane mirror 25, that is, the distance from the optical path of the laser beam before entering the plane mirror 25. Changes. Accordingly, by rotating the plane mirror 25 in the horizontal direction and the vertical direction, the incident position of the laser light incident on the rotary paraboloid mirror 26 is changed in the horizontal direction and the vertical direction, so that the optical axis of the wide-angle photographing lens 11 is changed. Within the vertical plane, the laser beam can be scanned in two directions (horizontal direction and vertical direction) perpendicular to each other, whereby the illumination position of the laser beam can be shifted in the two directions.

  Even when the rotation center O of the plane mirror 25 slightly deviates from the surface center of the plane mirror 25, the focal position of the rotary paraboloid mirror 26 and the rotation center O coincide with each other, and the condensing lens 28 collects light. The point (imaging point) may be aligned with the rotation center O.

  FIG. 7 is an explanatory diagram showing another configuration of the laser beam scanning mechanism 14 of the present embodiment. The laser beam scanning mechanism 14 may have a configuration in which an AOD 29 is disposed in place of the flat mirror 25 and a drive circuit 30 (second drive circuit) is disposed in place of the mirror rotating mechanism 27. A portion 29 a of the AOD 29 is at the focal position of the rotary paraboloid mirror 26. The AOD 29 diffracts and reflects the laser light from the laser light source 2 at the part 29 a and guides it to the rotary paraboloid mirror 26.

  The drive circuit 30 is a drive circuit that applies an ultrasonic wave (signal) to the crystal of the AOD 29, and changes the diffraction angle of the laser light at the AOD 29 by changing the frequency of the ultrasonic wave applied to the crystal of the AOD 29. The incident position of the laser beam incident on the rotary paraboloid mirror 26 is changed.

  In the above configuration, the laser light emitted from the laser light source 2 and incident on the part 29 a of the AOD 29 via the condenser lens 28 is diffracted and reflected there and then incident on the rotary paraboloid mirror 26. By changing the frequency of the ultrasonic wave applied to the AOD 29 by the drive circuit 30, the diffraction angle of the laser light diffracted and reflected by the AOD 29 is changed. Thereby, the rotating paraboloid mirror 26 of the diffracted and reflected laser light is changed. The position of incident light changes. At this time, since a portion 29a of the AOD 29 is at the focal position of the rotary paraboloid mirror 26, the laser light reflected by the portion 29a of the AOD 29 and incident on each position of the rotary paraboloid mirror 26 is reflected there. And emitted in the same direction (in a direction parallel to each other). Accordingly, even in this case, the height of the laser light reflected by the rotary paraboloid mirror 26 changes according to the frequency of the ultrasonic wave applied to the AOD 29. As a result, the laser beam can be scanned in the height direction. Note that scanning in both the horizontal and vertical directions may be performed by the AOD 29, only scanning in one direction may be performed by the AOD 29, and scanning in the other direction may be performed by a rotation mechanism (not shown).

[Embodiment 4]
FIG. 8 is a block diagram showing a configuration of a main part of the monitoring system 1 according to still another embodiment of the present invention. The monitoring system 1 of the present embodiment is a system to which the configuration described in the first to third embodiments can be applied. In addition to the laser light source 2, the image sensor 4, the laser light scanning mechanism 14, and the like, an image recognition unit 31, a distance measuring unit 32, a notification unit 33, a communication unit 34, and a control unit 35.

  The control unit 35 is a block that controls the operation of each unit of the monitoring system 1, and includes, for example, a central processing unit (CPU). Note that the image recognition unit 31 and the distance measurement unit 32 described above may be configured integrally with the control unit 35, or may be configured by another calculation unit or a circuit that performs specific processing.

  The image recognition unit 31 is a block for recognizing a suspicious person or a suspicious object by performing an image recognition process on image data of an image captured and acquired by the imaging sensor 4. In the image recognition process, for example, the contour of an object (including a person, a bicycle, a motorcycle, a car, an unmanned airplane, etc.) is extracted from the image data of the image acquired by the imaging sensor 4 and pattern matching is performed. The process of recognizing the shape by such a method is included. By such image recognition processing, it is possible to recognize the approach or intrusion of an object and determine whether it is a suspicious person or a suspicious object.

The distance measuring unit 32 is a block that measures the distance from the monitoring system 1 to an object. For example. When the control unit 35 causes the laser light source 2 to emit light in a pulse and drives the shutter of the image sensor 4 in synchronization with the pulse emission, the distance measuring unit 32 reflects the laser light output by the pulse light emission by the object. Time T (sec) until it enters the image sensor 4 is measured. Therefore, the distance measuring unit 32 can measure the distance S (= T × V) to the object from the time T and the speed of light V (for example, 3 × 10 ⁸ m / sec) (so-called Time of). Flight (TOF) method).

  The notification unit 33 is a block for notifying the outside when a suspicious person or a suspicious object is recognized by the image recognition in the image recognition unit 31, for example, an output unit (buzzer, speaker) that outputs sound or sound. Etc.). The communication unit 34 is a part serving as an interface for outputting information to the outside when a suspicious person or a suspicious object is recognized by the image recognition by the image recognition unit 31, and is a communication line (such as the Internet). Wired or wireless).

  FIG. 9 is a flowchart showing an operation flow in the monitoring system 1 of the present embodiment. In the regular monitoring (S1 to S4), the approach and intrusion of a suspicious person or a suspicious object (hereinafter also referred to as a suspicious person) such as a person, a bicycle, a motorcycle, or a car is detected by the image recognition processing in the image recognition unit 31. Processing is in progress.

  That is, in the steady monitoring, the far field is photographed by the imaging sensor 4 under the scanning of the laser beam by the laser beam scanning mechanism 14 (S1). At this time, it is desirable to take a photograph by illuminating a distant place with a laser beam of visible light and near-infrared light in the daytime and illuminate a distant place with a laser beam of near-infrared light at night. Near-infrared light is light that cannot be seen by human eyes, so it is possible to take pictures of distant places without being noticed by suspicious people, etc., and it is possible to consider the neighborhood. You do n’t have to be realized.)

  Next, the image recognition unit 31 performs image recognition processing on an image acquired by photographing with the imaging sensor 4 (S2). As a result of S2, when the image recognition unit 31 recognizes the presence of a suspicious person or the like (Yes in S3), the control unit 35 operates the notification unit 33 to notify (warn) the presence of the suspicious person or the like to the surroundings. At the same time, information indicating that a suspicious person or the like has entered is transmitted to the outside (for example, a security company) via the communication unit 35 (S4).

  Note that, for example, a 30 cm square object at a distance of 200 m from the monitoring system 1 is photographed in the range of 1.5 × 1.5 pixels by the imaging sensor 4. If the object has such a size, the image recognition unit 31 can detect the object. Further, when an object crosses the imaging range, even if the object crosses in a straight line at a speed of 50 km per hour in a vertical direction shorter than the horizontal direction, the object can be imaged by the imaging sensor 4 for about 160 seconds. Therefore, the image recognition unit 31 can recognize the identity of the object by image recognition or the like during the photographing.

  On the other hand, if the image recognition unit 31 does not recognize the presence of a suspicious person or the like as a result of S2 (No in S3), it may be difficult to recognize, so the routine monitoring is shifted to S5. . Here, the case where it is difficult to recognize the presence of a suspicious person or the like is a case where, for example, there are unclear parts in a captured image or there is an image of a small object, and the image recognition process cannot clearly recognize it as a suspicious person or the like. Can be assumed.

  In S <b> 5, the control unit 35 causes the laser light source 2 to emit light in pulses and drives the shutter of the image sensor 4 in synchronization with the pulse emission. Then, the distance measuring unit 32 measures the time until the laser light output by the pulse emission is reflected by the distant object and enters the image sensor 4 to measure the distance to the object (S6). Thereafter, the image recognition unit 31 determines the presence or absence of a suspicious person or the like based on the result of the image recognition process in S2 and the distance measured by the distance measurement unit 32 in S6 (S7). The above-mentioned distance measurement reveals the approximate size and shape of the photographed object, so it is easy to determine whether the object is a suspicious person who should be careful or is harmless, such as an insect or bird. It becomes possible to judge.

  In S7, when the image recognition unit 31 determines that there is a suspicious person or the like (Yes in S7), the process proceeds to S4 to notify the surrounding of the existence of the suspicious person and to the outside. Information transmission is performed (S4). On the other hand, when the image recognition unit 31 determines in S7 that there is no suspicious person or the like (No in S7), the control unit 35 changes the light emission of the laser light source 2 from pulse emission to normal emission (always emission). (S8), and thereafter, the process returns to S1 and the subsequent processing is repeated.

  As described above, the image recognition unit 31 performs image recognition processing on the image captured in S1 to recognize suspicious persons and the like (S2 and S7). It is possible to distinguish them from plants, leaves, garbage, etc.), and to realize an advanced monitoring system 1.

  In addition, in important facilities such as public infrastructure (infrastructure; facilities established as a base for industry and life) and public buildings, intruders are often monitored 24 hours a day. In such a facility, it is conceivable that an alarm indicating that there is an intruder frequently is issued by an object that does not cause harm (such as the above-described garbage). In such a case, the person who is guarded by the monitoring system must take some action and confirm that it is a false alarm one by one. Sometimes it is necessary to rush to the place where you think you have invaded to find the cause of the false alarm.

  On the other hand, in the monitoring system 1 of the present embodiment described above, by using the image sensor 4 and making full use of the image recognition unit 31, it is divided into harmless ones and those that may be harmful in advance. Because it can be recognized, it is possible to minimize the need for security guards to rush to the site due to misinformation.

  The image recognizing unit 31 was photographed in S7 in order to determine the presence or absence of a suspicious person or the like based on the result of the image recognition process described above and the distance measured by the distance measuring unit 32. Even when the image of the object is unclear or the image of the object is small, it is possible to determine the presence or absence of a suspicious person or the like by grasping the approximate size or shape of the object. As a result, the monitoring system 1 can improve the monitoring accuracy of suspicious persons, etc., and perform more advanced monitoring.

[Supplement]
In the above, an example in which a light source that emits laser light having an intensity peak near a wavelength of 900 nm is used as the illumination laser light source 2 is described. However, the laser light source to be used is not limited to this. For example, it is possible to use a light source that emits a laser beam having an intensity peak in the vicinity of a wavelength of 780 nm or 820 nm. However, it is necessary to use a light source that emits laser light in a wavelength range in which the imaging sensor 4 has sufficient sensitivity.

  Further, when it is desired to inform the surroundings that the image is being taken, a light source that emits visible light as the laser light may be used. This is because notifying the surroundings of shooting is also effective for crime prevention and intimidation. At that time, a light source that emits a laser beam having a wavelength of about 450 nm or 650 nm, or a laser light source in the vicinity of green that has been modulated to change its wavelength to visible light and has good visibility may be used.

  Since the imaging sensor 4 only needs to have sensitivity in at least one wavelength region of visible light and near infrared light, a sensor having sensitivity from the visible region to the near infrared region can be used as the imaging sensor 4. However, it is also possible to use a sensor dedicated to the near infrared. The near-infrared sensor has a high sensitivity near 900 nm used for illumination, and photography is possible even if the output of laser light is suppressed. In the near-infrared light shooting, the image is displayed in monochrome, but is similar to the monochrome display in visible light shooting, so that it is recognized without a sense of incongruity when confirmed by a person.

  In the monitoring system 1 described above, the laser light source 2 is used as a light source for illumination, and an LED or a small semiconductor laser is not used. Since LEDs are light sources that have irregular wavelengths and phases and light diverges, even a very high-power bright LED can illuminate only about 20 m at most. Further, the semiconductor laser has a small output, and even if the phase and wavelength are uniform, it is insufficient for illuminating a distant place of 100 m to 300 m.

  In the monitoring system 1 described above, the concave lens 13 increases the beam width of the laser beam so that the area of the illumination beam by the laser beam is about 1/100 of the area of the entire imaging range by the imaging sensor 4. However, the extent to which the light flux width is expanded is not limited to the above example. For example, in the configuration shown in FIG. 1, when the output of the laser light source 2 is large and the driving speed of the flat plate rotation mechanism 22 is slow, the luminous flux width is set so that the area of the illumination luminous flux is larger than 1/100 described above. When the output of the laser light source 2 is small and the driving speed of the flat plate rotation mechanism 22 is high, the beam width is expanded so that the area of the illumination beam is smaller than 1/100 described above. Also good.

  The wide-angle photographing lens 11 used in each embodiment is not a special one, and a commercially available one can be used. A lens system for a 1/6 inch diagonal image sensor with a horizontal angle of view of 90 ° is available in a lineup of commercially available products. An optical path synthesizing member (optical path branching element) such as an optical path synthesizing prism 12 is inserted between the lens system and the image sensor. However, in most optical systems close to image side telecentric, a sufficient lens back is ensured. Therefore, it is easy to insert such an optical path combining member.

  Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the invention.

  The present invention can be used, for example, in a monitoring system that monitors the presence or absence of an object at a distance of 100 m to 300 m from a building.

DESCRIPTION OF SYMBOLS 1 Monitoring system 2 Laser light source 3 Illumination optical system 4 Imaging sensor 11 Wide angle imaging lens 12 Optical path synthesis prism (optical path synthesis member)
12 'optical path combining element (optical path combining member)
14 Laser beam scanning mechanism 21 Parallel plate (first parallel plate)
22 Flat plate rotation mechanism 23 Parallel plate (second parallel plate)
23a surface (incident surface)
23b surface (outgoing surface)
23 'AOD (acousto-optic device)
24a Slide mechanism 24c Drive circuit (first drive circuit)
25 Planar mirror 26 Rotating parabolic mirror 27 Mirror rotation mechanism 29 AOD (acousto-optic device)
30 Drive circuit (second drive circuit)
31 Image recognition unit 32 Distance measurement unit 35 Control unit

Claims (11)

A wide-angle photographic lens having a diagonal half angle of view ω of 30 ° or more and a substantially telecentric image side;
An imaging sensor having a sensitivity in at least one wavelength region of visible light and near-infrared light, and imaging an imaging target located at a distance of 100 m to 300 m via the wide-angle imaging lens;
A laser light source that emits laser light having an intensity peak in the wavelength range in which the imaging sensor has sensitivity;
An illumination optical system that guides the laser light emitted from the laser light source to the imaging target side;
The wide-angle photographing lens also serves as a part of the illumination optical system,
The illumination optical system scans the laser light emitted from the laser light source and incident on the wide-angle photographing lens, and thereby the photographing range of the photographing target photographed by the imaging sensor via the wide-angle photographing lens. And a laser beam scanning mechanism that sequentially shifts the illumination position of the laser beam that illuminates a part of the imaging range via the wide-angle imaging lens.   The illumination optical system includes an optical path combining member that combines an optical path of the laser light emitted from the laser light scanning mechanism with an optical path of light incident on the imaging sensor from the imaging target side through the wide-angle imaging lens. The monitoring system according to claim 1, further comprising: causing the laser light to enter the wide-angle photographing lens through the optical path combining member. The laser beam scanning mechanism is
A first parallel plate disposed on the light emitting side of the laser light source;
The monitoring system according to claim 2, further comprising a flat plate rotating mechanism that rotates the first parallel flat plate. The laser beam scanning mechanism is
A second parallel plate positioned so that the laser light from the laser light source is vertically incident;
A slide mechanism that slides the second parallel flat plate in a direction perpendicular to the thickness direction;
Two opposite surfaces of the second parallel plate, wherein the laser light incident surface and the light exit surface are diffractive surfaces, respectively;
The diffraction characteristics of each diffraction surface are such that the diffraction angle continuously changes depending on the incident position of the laser beam in the sliding direction perpendicular to the thickness direction of the second parallel plate, and is perpendicular to the incident surface. The monitoring system according to claim 2, wherein the incident laser beam is set to be emitted vertically from the emission surface. The laser beam scanning mechanism is
An acousto-optic element;
A first drive circuit that applies ultrasonic waves to the crystal of the acoustooptic device,
The first drive circuit changes a diffraction angle of the laser beam incident on the acoustooptic device by changing a frequency of ultrasonic waves applied to the crystal of the acoustooptic device, and changes the laser beam to the laser beam. The monitoring system according to claim 2, wherein the monitoring system emits light. The laser beam scanning mechanism includes a plane mirror, a paraboloid mirror, and a mirror rotation mechanism that rotates the plane mirror.
The center of rotation of the plane mirror is at the focal position of the paraboloid mirror,
The plane mirror reflects the laser light from the laser light source at the rotation center and guides it to the rotary paraboloid mirror.
The monitoring system according to claim 2, wherein the mirror rotation mechanism changes the incident position of the laser light incident on the rotary paraboloidal mirror by rotating the plane mirror. The laser beam scanning mechanism includes an acoustooptic device, a paraboloid mirror, and a second drive circuit that applies ultrasonic waves to the crystal of the acoustooptic device,
A portion of the acousto-optic element is at the focal position of the rotating parabolic mirror;
The acousto-optic device diffracts and reflects the laser light from the laser light source at the part and guides it to the rotary paraboloid mirror,
The second drive circuit changes the diffraction angle of the laser light by changing the frequency of ultrasonic waves applied to the crystal of the acoustooptic device, and enters the rotary paraboloid mirror. The monitoring system according to claim 2, wherein the incident position of the light is changed.   8. The monitoring according to claim 1, wherein the laser beam scanning mechanism scans the laser beam in two directions perpendicular to each other in a plane perpendicular to the optical axis of the wide-angle imaging lens. 9. system.   2. An image recognition unit for recognizing a suspicious person or a suspicious object by performing image recognition processing on image data of an image captured and acquired by the imaging sensor. The monitoring system according to any one of 8 to 8. A control unit for causing the laser light source to emit light and driving a shutter of the imaging sensor in synchronization with the pulse emission;
A distance measuring unit that measures a time from when the laser light output by the pulsed light emission is reflected by the object to be imaged and incident on the imaging sensor, and measures a distance to the object; And
The said image recognition part judges the presence or absence of a suspicious person or a suspicious object based on the result of the said image recognition process, and the distance measured in the said ranging part, The characterized by the above-mentioned. The monitoring system described. The wavelength range of the visible light is 450 nm or more and 650 nm or less,
11. The monitoring system according to claim 1, wherein a wavelength range of the near infrared light is 780 nm or more and 1000 nm or less.

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