A smoke and fog penetration imaging device and method based on near infrared band

Abstract

The present invention provides a smoke and fog-penetrating imaging device and method based on a near-infrared band, which relates to the technical field of imaging equipment, and includes: a light source and a camera arranged on the left and right sides of a helmet, wherein the light source and the camera are connected via a synchronization signal line; the light source is a near-infrared laser line scanning light source, and the light source includes a semiconductor infrared laser, a galvanometer, a collimating lens, and a Powell prism; the camera is a near-infrared camera with a rolling shutter exposure function, and the camera includes a near-infrared image sensor and a synchronization signal module, and the exposure mode of the near-infrared image sensor is a rolling shutter form, and the output of the synchronization signal module includes a field synchronization signal and a line synchronization scanning signal. In the present invention, the backscattered light entering the near-infrared camera is reduced by the near-infrared laser line scanning light source and the near-infrared camera rolling shutter mode, and the influence of backscattering on image contrast and clarity is reduced from an optical perspective, thereby improving the imaging quality from the source.

Description

Technical Field

[0001] The present invention relates to the technical field of imaging equipment, and in particular to a smoke and fog penetrating imaging device and method based on a near-infrared band. Background Art

[0002] Visual detection at the fire scene directly affects fire rescue, but the fire environment with low visibility makes it difficult for rescuers to quickly and accurately identify information in the fire, so that people in distress cannot be rescued in time. The incomplete combustion of the combustibles in the fire produces a large amount of smoke, which causes the visibility of the human eye to plummet, making the originally very familiar environment unrecognizable. The particles generated by the combustion of the fire environment have a great influence on the imaging quality of the equipment due to their optical properties. The influence is mainly manifested in the scattering of light by smoke particles. The scattering effect of smoke particles reduces the contrast of infrared imaging. Therefore, one of the key technologies in the field of fire rescue is to achieve clear imaging of people and objects in low visibility.

[0003] At present, there are three main technical approaches to alleviate smoke particle scattering from an optical perspective: polarization imaging technology, distance-gated imaging technology, and light path overlap reduction technology. At present, the most direct way to reduce scattering is to reduce the light path overlap technology, reduce the overlap area between the light source and the camera light path, and the placement relationship between the light source and the camera is shown in Figure 1. In Figure 1 (a), when the camera and the light source are adjacent, there is a large overlap between the camera and the light source light path area, the scattering area 11 becomes larger, and the backscattering light is more strongly affected. In Figure 1 (b), the light source and the camera are separated by a certain distance, the light path overlap area is reduced, the scattering area 11 becomes smaller, and the backscattering effect is reduced. The degree of reduction is positively correlated with the distance between the camera and the light source, but the large distance between the light source and the camera is not conducive to the actual installation and operation. In Figure 1 (c), the light source and the camera light path do not overlap at all, and only the scattered light 5 on the light source path is used to illuminate part of the camera's field of view. Since there is no overlap between the camera and the light source light path, the backscattering effect is minimized, but this method requires a significant increase in the power of the light source to illuminate the target surface.

[0004] In the technology of reducing light path overlap, in order to further reduce the overlap of light paths, patent CN106534632A proposed a "synchronous scanning imaging system", but the system requires that the installation distance between the light source and the camera be greater than 1 / 2 of the farthest imaging distance, and after the installation position is determined, the system can only image the target surface at a fixed distance. In order to solve this problem, invention CN109581787A proposed "an underwater imaging device and method using laser point scanning". This method uses a two-dimensional laser point scanning light source and a CMOS camera with rolling shutter exposure to illuminate the camera's instantaneous field of view through point-shaped laser synchronous scanning. This method requires that the horizontal scanning frequency of the two-dimensional laser scanning be as high as possible. In addition, when the horizontal scanning frequency of the two-dimensional laser scanning is increased, the horizontal scanning frequency of the two-dimensional laser scanning is increased.

[0005] The horizontal scanning frequency must reduce the size of the reflector, and the light spot is concentrated on a reflector of about 1 mm. 5 will cause the internal components of the reflector to burn out, which limits the effective detection distance. In order to overcome this shortcoming,

[0006] Patent CN113596298A proposes "an underwater laser synchronous field scanning imaging device and method", which mainly includes a linear laser source and an sCMOS image sensor camera with rolling shutter exposure. The linear laser source is used to synchronously scan and illuminate the instantaneous field of view, thereby reducing the backscattering effect in underwater imaging.

[0007] In summary, the above methods have achieved good results in underwater backscattering, but they are not applicable to imaging through smoke and fog in low visibility. There are several reasons for this. First, the above methods are all aimed at the influence of underwater backscattering, so the light sources used are all visible light, specifically blue or green light sources, in order to reduce the attenuation effect of particles in the water on the laser. However, in imaging through smoke and fog, more factors that need to be considered are scattering effects, and blue and green lasers are difficult for the human eye to see.

[0008] Therefore, a longer wavelength light source should be used in smoke and fog imaging. On the one hand, it can reduce the backscattering effect, and on the other hand, it can avoid damage to the human eye.

[0009] The cameras used in the above methods are all CMOS cameras in the visible light band, and the cameras described in the above methods have not been optimized for near-infrared band imaging. Therefore, when using near-infrared light sources in the air, there is a serious lack of response and a decrease in sensitivity.

[0010] In the position relationship, the light source and the camera are installed up and down, which will occupy a large vertical space and is difficult to be applied to wearable devices. Therefore, the technologies involved in the above three inventions are

[0011] None of them can be applied in the field of smoke and fog imaging in fire scenes. Summary of the invention

[0012] Based on the above-mentioned technical problem that the image contrast of near-infrared imaging equipment drops by 5 degrees during fire rescue, dense smoke and fog environments, and the effective detection distance is insufficient, a smoke and fog-penetrating imaging device and method based on the near-infrared band are provided, which can greatly reduce the backscattering effect in the near-infrared band smoke and fog-penetrating imaging.

[0013] The technical means adopted by the present invention are as follows:

[0014] A smoke and fog penetrating imaging device based on a near-infrared band, comprising: a light source and a camera arranged on the left and right sides of a helmet, wherein the light source and the camera are connected via a synchronization signal line;

[0015] The light source is a near-infrared laser line scanning light source, which includes a semiconductor infrared laser, a galvanometer, a collimating lens and a Powell prism. The semiconductor infrared laser generates a beam of near-infrared laser, which is converted into parallel laser through the collimating lens. The parallel laser beam is formed into a linear laser through the Powell prism. The linear laser is reflected onto the target surface through the galvanometer to form a linear light spot. The galvanometer performs one-dimensional swing under the control of a galvanometer driving signal.

[0016] The camera is a near-infrared camera with a rolling shutter exposure function, and includes a near-infrared image sensor and a synchronization signal module. The exposure mode of the near-infrared image sensor is a rolling shutter form. The near-infrared image sensor realizes rolling exposure of the imaging surface with a strip-shaped exposure area. The output of the synchronization signal module includes a field synchronization signal and a line synchronization scanning signal; when the near-infrared image sensor is exposed in the rolling shutter form, the synchronization signal module simultaneously outputs a field synchronization signal.

[0017] Furthermore, the strip-shaped exposure field of view is consistent with the moving direction of the strip-shaped exposure area, and the number of rows of the strip-shaped exposure area is controlled by the exposure time. When the exposure time decreases, the strip-shaped exposure area becomes narrower, and at the same time, the strip-shaped exposure field of view on the target surface becomes narrower, and the strip-shaped exposure field of view completes a rolling scan of the target surface.

[0018] Furthermore, the line synchronization signal is sent to the microcontroller through the synchronization circuit module, and the microcontroller changes the oscillation angle of the galvanometer by controlling the galvanometer driving signal, thereby causing the galvanometer to oscillate in one dimension.

[0019] Furthermore, the swing direction of the linear light spot is consistent with the moving direction of the exposure field of the camera, so that the instantaneous exposure field of view on the target surface is illuminated in sequence, and then the entire field of view is illuminated by the light source.

[0020] Furthermore, the lighting methods of the light source include direct infrared lighting method and indirect infrared lighting method. The near-infrared laser line scanning area of ​​the direct infrared lighting method coincides with the camera exposure area, while the near-infrared laser line scanning area of ​​the indirect infrared lighting method does not coincide with the camera exposure area. The exposure area is infrared illuminated by scattered light on the near-infrared laser path.

[0021] The present invention also provides a method for imaging through smoke and fog based on a near-infrared band, which is implemented based on any of the above-mentioned imaging devices for imaging through smoke and fog based on a near-infrared band, and comprises the following steps:

[0022] The image sensor starts to expose with a rolling shutter, and the synchronization signal module sends a field synchronization signal to the synchronization circuit module in the light source;

[0023] The synchronization circuit module receives the field synchronization signal and sends a timing pulse to the microcontroller in the light source;

[0024] The microcontroller controls the infrared laser to emit laser light, and the laser light is reflected by the galvanometer and irradiated onto the imaging target surface, and the laser light forms a linear laser spot on the target surface, and the linear laser spot coincides with the exposure field of view of the image sensor;

[0025] The synchronization signal module buffers the row synchronization scanning signal of the reset register inside the image sensor and sends it to the light source through the synchronization signal line;

[0026] The light source receives a line synchronization scanning signal and changes the angle of the reflector in the galvanometer, so that the linear laser spot moves in the same direction as the exposure field in the camera and keeps overlapping until one exposure is completed;

[0027] When the linear laser spot moves to the leftmost end of the target surface, the synchronization signal module sends a field blanking signal to the light source;

[0028] After receiving the field blanking signal, the light source controls the infrared laser module to stop outputting laser light, and the galvanometer driver controls the galvanometer reflection angle to change so that the galvanometer angle returns to the field start position.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] 1. Optical backscattering capability. In the present invention, the backscattered light entering the near-infrared camera is reduced by a near-infrared laser line scanning light source and a near-infrared camera rolling shutter, which reduces the impact of backscattering on image contrast and clarity from an optical perspective and improves the quality of imaging from the source;

[0031] 2. The imaging system has a compact structure and can be used as a wearable device. The light source in the present invention adopts a linear near-infrared light source, and the light path of the light source is extremely narrow, so the light source and the camera can be placed more compactly, and can be installed on both sides of the helmet of the wearer;

[0032] 3. The present invention can greatly reduce the overlap area of ​​the optical path between the camera and the near-infrared laser line scanning light source by setting the direct lighting mode of the light source, and reduce the impact of smoke scattering. The present invention sets the indirect lighting mode of the light source, relying on the scattered light on the near-infrared laser path to infrared illuminate the exposure area. This lighting method does not overlap the optical path, and the scattering effect is minimal.

[0033] 4. The camera of the present invention adopts a rolling shutter exposure mode to form a strip-shaped exposure field on the target surface, which greatly reduces the volume of light path overlap with the light spot emitted by the linear laser scanning light source.

[0034] 5. The present invention uses near-infrared laser, which has a longer wavelength and will not cause harm to human eyes. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0036] FIG1 is a schematic diagram of the macro-angle light source and camera placement and the degree of overlap of the optical path; Figure 1a This is a schematic diagram showing that the light source and the camera are placed close together, with the light paths overlapping over a large area; Figure 1b This is a schematic diagram showing that the light source and the camera are placed far apart, reducing the overlap range of the light paths; Figure 1c The light source and the camera are placed close to each other, the light paths do not overlap, and scattered light is used for lighting.

[0037] Figure 2 It is a schematic diagram of the device of the present invention.

[0038] Figure 3 It is a schematic diagram of the internal structure of the camera of the present invention.

[0039] Figure 4 Schematic diagram of the internal structure of the light source of the present invention.

[0040] Figure 5 It is a timing diagram of the operation process of the device of the present invention.

[0041] In the figure: 1. Camera; 2. Light source; 3. Helmet; 4. Synchronous signal line; 5. Scattered light; 6. Light path; 7. Target surface; 8. Light spot; 9. Exposure field of view; 10. Co-directional movement; 11. Scattering area. DETAILED DESCRIPTION

[0042] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0043] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0045] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, the numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be clear that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship. The technology, methods and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be regarded as part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0046] The present invention provides a smoke and fog penetrating imaging device based on the near infrared band, such as Figure 2-5 As shown, the device is composed of a light source 2, a camera 1, and a helmet 3. The helmet 3 is not the only embodiment of the present invention, and other carriers such as a headband and a chest strap may also be used. The light source 2 is a near-infrared laser line scanning light source, and the camera 1 is a near-infrared camera with a rolling shutter exposure function. The light source 2 is installed on one side of the helmet 3 of the wearer, and the camera 1 is installed on the other side of the helmet 3 of the wearer, and the camera 1 is connected to the light source 2 through a synchronization signal line 4.

[0047] The near-infrared laser line scanning light source 1 is composed of a semiconductor infrared laser (IRlaser) and a galvanometer. The galvanometer is controlled by a galvanometer driving signal and swings under the control of the galvanometer driving. Its swinging process is a one-dimensional swing controlled by the driving signal. The semiconductor infrared laser generates a beam of near-infrared laser, which is converted into a parallel laser through a collimating lens. The parallel laser beam passes through a Powell prism to form a linear laser, and finally is reflected to the target surface through a galvanometer to form a linear light spot 8. As the galvanometer swings, the linear light spot 8 illuminates the camera exposure field 9 in turn, thereby realizing the illumination of the exposure field 9 of the camera 1. The near-infrared camera includes a near-infrared image sensor and a synchronization signal module, and the exposure mode of the near-infrared image sensor is a rolling shutter. The rolling exposure is realized on the imaging surface with a strip-shaped exposure area. When the exposure area is exposed, a strip-shaped exposure field of view 9 will be formed on the target surface 7. The strip-shaped exposure field of view 9 is consistent with the moving direction of the exposure area. The number of lines in the exposure area is controlled by the exposure time. When the exposure time is reduced, the exposure area becomes narrower, and the strip-shaped exposure field of view 9 on the target surface will also become narrower. As the strip-shaped exposure field of view 9 completes a rolling scan of the target surface. The near-infrared camera completes an exposure process and forms a frame. The output of the near-infrared camera synchronization signal module consists of two parts: a field synchronization signal and a line synchronization scanning signal. When the near-infrared camera sensor starts to expose in the form of a rolling shutter, the near-infrared camera synchronization signal module will send a field synchronization signal. After receiving the field synchronization signal, the near-infrared laser line scanning light source 2 is turned on, and the near-infrared laser line scanning light source 2 forms a linear spot 8 on the target surface. The linear spot 8 is located at the beginning of the exposure area. The line synchronization signal controls the size of the galvanometer drive signal of the near-infrared laser line scanning light source 2, and changes the galvanometer swing angle through the driving voltage. As the galvanometer angle changes, the linear laser spot 8 swings on the target surface. The swing of the linear light spot 8 is consistent with the moving direction of the exposure field of view 9 of the near-infrared camera, and then the instantaneous exposure field of view 9 on the target surface is illuminated in sequence, achieving the effect of the entire field of view being illuminated by the light source 2. Since the optical path 6 of the laser line light source 2 is extremely small, and the near-infrared laser line scanning light source 2 can only illuminate an extremely narrow instantaneous exposure field of view 9 in the near-infrared camera rolling shutter imaging, the overlap range of the light source 2 and the camera field of view 9 reaches an extremely low level, thereby greatly reducing the influence of backscattering on near-infrared imaging.

[0048] The near-infrared laser line scanning light source 2 described in the invention, when receiving the field synchronization signal sent by the near-infrared camera, the near-infrared laser line scanning light source 2 is turned on, and then the camera row exposure field 9 is scanned in sequence under the control of the camera row synchronization signal. There are two ways to achieve infrared lighting. The first is direct infrared lighting, that is, the near-infrared laser line scanning area coincides with the camera row exposure area, which can greatly reduce the overlap area of ​​the optical path 6 of the camera 1 and the near-infrared laser line scanning light source 2, and reduce the impact of smoke scattering. The second method is indirect infrared lighting, the near-infrared laser line scanning area does not coincide with the camera exposure area, and the exposure area is infrared illuminated by the scattered light on the near-infrared laser path. In this lighting method, the optical path 6 does not overlap, and the scattering effect is extremely small, but it needs to be used with a high-power near-infrared laser.

[0049] The present invention also provides a smoke and fog-penetrating imaging method based on the near-infrared band, which mainly utilizes the reduction of the overlapping volume of the optical path 6 between the light source 2 and the camera 1, and the characteristics of the near-infrared laser having good smoke and fog-penetrating capabilities, and proposes a smoke and fog-penetrating imaging method and device based on the near-infrared band, which can clearly image the target object under low visibility conditions such as thick smoke and fog.

[0050] The near-infrared laser line scanning light source 2 is placed on the left side of the helmet 3, and the near-infrared camera is placed on the right side of the helmet 3, but this is not the only way to place them, and the positions of the two can be interchanged. The components related to the present invention in the near-infrared laser line scanning light source 2 are the infrared laser module and the microcontroller module, as well as the galvanometer drive module and the synchronization signal module. The components related to the present invention in the near-infrared camera 1 are the image sensor module and the synchronization signal module. When the near-infrared camera image sensor starts to expose with a rolling shutter, the near-infrared camera synchronization signal module will send a field synchronization signal to the synchronization circuit module in the near-infrared laser line scanning light source 2. The synchronization circuit module receives the field synchronization signal and sends a timing pulse to the microcontroller. The microcontroller controls the infrared laser to emit a laser, which is reflected by the galvanometer and irradiated onto the imaging target surface 7, forming an optical path 6 in space, and forming a linear laser spot 8 on the target surface. The linear laser spot 8 coincides with the exposure field of view 9 of the camera image sensor. After the near-infrared camera synchronization signal module buffers the line synchronization scanning signal of the reset register inside the image sensor, it is forwarded to the near-infrared laser line scanning light source 2 through the camera and near-infrared laser line scanning light source synchronization signal line 4, which is used to control the change of the reflector angle in the galvanometer, so that the linear laser spot 8 and the exposure field 9 in the camera move in the same direction 10 and keep overlapping until one exposure is completed. The near-infrared laser line spot 8 runs to the leftmost end of the object plane, and the near-infrared camera synchronization signal module sends a field blanking signal. After the near-infrared laser line scanning light source 2 receives the signal, the infrared laser module stops outputting the laser, and the galvanometer drive controls the galvanometer reflection angle to change, and the galvanometer angle returns to the field start position. Camera 1 completes one frame of imaging and prepares for the next frame of imaging. By adjusting the field start signal and the blanking signal time, the requirements of the mainstream video format (such as the BT.1120 video specification specified by ITU-R) can be met, so that it can be applied to the field of near-infrared video imaging.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A smoke and fog penetrating imaging device based on near infrared band, characterized in that: Applicable to smoke and fog imaging environment, including: light sources and cameras arranged on the left and right sides of the helmet, the light sources and cameras are connected via a synchronization signal line; The light source is a near-infrared laser line scanning light source, which includes a semiconductor infrared laser, a galvanometer, a collimating lens and a Powell prism. The semiconductor infrared laser generates a beam of near-infrared laser, which is converted into parallel laser through the collimating lens. The parallel laser beam is formed into a linear laser through the Powell prism. The linear laser is reflected onto the target surface through the galvanometer to form a linear light spot. The galvanometer performs one-dimensional swing under the control of a galvanometer driving signal. The swing direction of the linear light spot is consistent with the moving direction of the exposure field of the camera, so that the instantaneous exposure field of the target surface is illuminated in sequence, and then the entire field of view is illuminated by the light source; The illumination method of the light source includes direct infrared illumination method and indirect infrared illumination method. The near-infrared laser line scanning area of ​​the direct infrared illumination method overlaps with the camera exposure area, while the near-infrared laser line scanning area of ​​the indirect infrared illumination method does not overlap with the camera exposure area, and the exposure area is infrared illuminated by scattered light on the near-infrared laser path; The camera is a near-infrared camera with a rolling shutter exposure function, comprising a near-infrared image sensor and a synchronization signal module. The exposure mode of the near-infrared image sensor is a rolling shutter form. The near-infrared image sensor implements rolling exposure of the imaging surface in a strip-shaped exposure area. The output of the synchronization signal module includes a field synchronization signal and a line synchronization scanning signal. When the near-infrared image sensor is exposed in the rolling shutter form, the synchronization signal module simultaneously outputs a field synchronization signal. The horizontal synchronization signal is sent to the microcontroller through the synchronization circuit module, and the microcontroller changes the oscillation angle of the galvanometer by controlling the galvanometer driving signal, thereby causing the galvanometer to oscillate in one dimension; The strip-shaped exposure field of view is consistent with the moving direction of the strip-shaped exposure area. The number of rows in the strip-shaped exposure area is controlled by the exposure time. When the exposure time decreases, the strip-shaped exposure area becomes narrower, and at the same time, the strip-shaped exposure field of view on the target surface becomes narrower, and the strip-shaped exposure field of view completes a rolling scan of the target surface.

2. A smoke and fog imaging method based on near infrared band, implemented based on the smoke and fog imaging device based on near infrared band as claimed in claim 1, characterized in that: The steps include: The image sensor starts to expose with a rolling shutter, and the synchronization signal module sends a field synchronization signal to the synchronization circuit module in the light source; The synchronization circuit module receives the field synchronization signal and sends a timing pulse to the microcontroller in the light source; The microcontroller controls the infrared laser to emit laser light, and the laser light is reflected by the galvanometer and irradiated onto the imaging target surface, and the laser light forms a linear laser spot on the target surface, and the linear laser spot coincides with the exposure field of view of the image sensor; The synchronization signal module buffers the row synchronization scanning signal of the reset register inside the image sensor and sends it to the light source through the synchronization signal line; The light source receives a line synchronization scanning signal and changes the angle of the reflector in the galvanometer, so that the linear laser spot moves in the same direction as the exposure field in the camera and keeps overlapping until one exposure is completed; When the linear laser spot moves to the leftmost end of the target surface, the synchronization signal module sends a field blanking signal to the light source; After receiving the field blanking signal, the light source controls the infrared laser module to stop outputting laser light, and the galvanometer driver controls the galvanometer reflection angle to change so that the galvanometer angle returns to the field start position.

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