First, the lens can not underestimate <br> <br> lens is the camera's eye, in order to adapt to different environments and monitoring requirements, the need to configure different specifications of the lens. For example, in indoor key surveillance, clear and large field of view image capture is required to configure a wide-angle lens; in an outdoor parking lot, it is necessary to see the whole picture of the parking lot and to be able to see the details of the car. This requires a wide angle. And the zoom lens, on the border line, the monitoring of the maritime defense line, requires ultra-long image capture.
1, the main parameters of the lens focal length (f): focal length is the distance between the lens and the photosensitive element, by changing the lens focal length, you can change the magnification of the lens, change the size of the captured image. When the object is far from the lens, we can use the following formula: Lens magnification, focal length/object distance. Increase the focal length of the lens, increase the magnification, can narrow the distance, the scope of the picture is small, the details of the vision can be seen more clearly; if the focal length of the lens is reduced, the magnification is reduced, the scope of the picture is enlarged, and See bigger scenes.
The main parameters of the lens field of view angle: In the actual project, we often use the horizontal field of view angle to reflect the shooting range of the screen. The larger the focal length f, the smaller the angle of view, and the smaller the range of the picture formed on the photosensitive element. Conversely, the smaller the focal length f, the larger the angle of view and the larger the range of the picture formed on the photosensitive element.
Aperture: The aperture is mounted on the rear of the lens. The larger the aperture is opened, the greater the amount of light that passes through the lens and the higher the image clarity. The smaller the aperture is opened, the smaller the amount of light that passes through the lens, and the sharper the image is. low. Usually expressed as F (light flux). F=focal length (f)/clear aperture. In the technical indicators of the camera, we can often see such parameters as 6mm/F1.4, which means that the focal length of the lens is 6mm, luminous flux is 1.4, then we can easily calculate the clear aperture of 4.29mm. In the case where the focal length f is the same, the smaller the F value and the larger the aperture, the greater the luminous flux reaching the CCD chip, and the better the lens.
2, the classification of the lens by the perspective of the size classification by aperture
Second, to improve the clarity of the image is to improve the camera's photosensitivity 1, the role of the photosensitive element Currently, the mainstream of the surveillance camera's photosensitive element using CCD components, in fact, is a photoelectric conversion element. Compared with previous CMOS sensor, CCD sensitivity is 3 to 10 times that of CMOS, so the CCD chip can receive more optical signals, converted into electrical signals, filtered and amplified by the video processing circuit to form the video signal output. . The stronger the received light signal, the greater the amplitude of the video signal. The video signal can be seen by connecting the video signal to the video input of a monitor or television. The only thing that improves the clarity of the image is to improve the camera's photosensitivity.
2. Configuration of lens and CCD sensor In Figure 1, we can see that the image formed on the CCD sensor is smaller than the original image. The dimensions of the imaging surface of the CCD chip are different, and the image size formed is also different.
CCD imaging size is commonly used 1/2 inch, 1/3 inch, CCD size specifications determine the camera's specifications.
Lens and CCD Sensor Configuration The CCD image size, which is the ratio of the camera frame width and height, is the same as the TV screen width and height ratio, which is usually 4:3. This ensures that the video image of the camera on the display is not distorted.
Lens specifications are also divided into 1/2 inch, 1/3 inch, etc., 1/2 inch lens can be used for 1/2 inch, 1/3 inch camera; 1/3 inch lens can only be used for 1/ A 3-inch camera cannot be used with a 1/2-inch camera because the 1/3-inch lens has a luminous flux of only 44% of the 1/2-inch lens's luminous flux and cannot meet the luminous flux requirements of a 1/2-inch camera.
The configuration of the focal length of the lens is still illustrated in Figure 1. Determining the appropriate focal length is an important factor in determining image quality. f=vD/Vf=hD/H. Where f represents the focal length, v represents the height of the CCD imaging dimension, V represents the height of the object being observed, h represents the width of the CCD imaging dimension, H represents the width of the object being observed, and D represents the distance from the object to the lens. Assume that a 1/3†CCD camera is used to observe the object to be measured with a width of 500 mm and a height of 400 mm. The focal point of the lens is 5000 mm from the object. It can be calculated by the formula: focal length f=4.8×5000/500≈48 mm or focal length f=3.6× 5000/400≈45mm.
Third, how to shoot in poor light conditions of the environment to clear image <br> <br> surveillance cameras can be requested in poor light conditions or even at night there is no light in the environment, but also to record clear images. In the indicator of the camera, we can often see the low illumination.
1. Illumination Concept The illuminance is a unit that measures the sensitivity of a camera and is expressed in Lux, which means that the camera can capture images under dim lighting conditions. The lower the value of Lux, indicates that the camera can take clear images under lower lighting conditions. We know that the nominal value of the video signal generated by the camera is 1v, and the standard value is 700mv. For example, if a lens with an aperture of F1.2 is used, the amplitude of the video signal output by the camera is the standard amplitude when the illuminance of the scene being shot is 0.02 Lux. The value of 700mv is 33%-50%. At this time, the minimum illumination of the camera is 0.02Lux/F1.2. The minimum illuminance of the test must pay attention to the aperture of the lens. The smaller the F value and the larger the aperture, the lower the illuminance required. Different apertures have different minimum illumination values.
2. Plan to achieve low illumination camera We know that CCD camera can be divided into color and black and white cameras. The minimum illumination of ordinary cameras is shown in the table below.
The minimum illuminance of ordinary cameras is visible light in the wavelength range of 380nm to 780nm. The wavelength of visible light is divided into red, orange, yellow, green, cyan, blue and violet from the longest to the shortest. The wavelength shorter than the violet light is called the ultraviolet light, and the wavelength is shorter than the infrared light. The long is called infrared light. The surface of the CCD sensor has a transparent UV-absorbing electrode, so the CCD cannot receive ultraviolet light. The CCD chip of an ordinary color camera has red, green, and blue filter bars, so the color camera cannot experience infrared light. However, the spectral range of ordinary CCD black-and-white cameras is very wide, and not only visible light but also infrared light can be felt.
Based on the above principles, engineers often use the following solutions to capture clear images in environments with poor lighting conditions.
(1) Ordinary low-intensity CCD black-and-white camera + infrared lamp Infrared radiation “lighting†is installed at the monitoring site to generate infrared light that cannot be seen by the human eye and can be captured by an ordinary camera. Night-time shooting can be achieved by a CCD black-and-white camera.
(2) Color to black and white video camera and infrared light The so-called color to black and white video camera refers to a daytime color camera. When the night lighting conditions are poor, the use of black and white images for high infrared sensitivity, automatically switches to black and white. Photographed with infrared rays. When combined with infrared light, the low-light camera must meet the minimum illumination supported by the infrared light.
(3) Infrared low-illumination color camera The infrared low-sensitivity color camera has an infrared sensitivity that is more than 4 times higher than that of a normal camera and can operate at zero illuminance (0 Lux).
Infrared low-illumination color camera (4) Low-speed shutter camera The low-speed shutter camera, also known as a screen-accumulating camera, continuously stores multiple frames (up to 128 frames) on a computer, resulting in poorly-lit and blurry pictures, and accumulates to become a clear picture. With SLOWSHUTTER technology, shooting under 0.008L/F1.2 illumination is achieved. This low-illuminance camera is suitable for museums that prohibit the destruction of red and ultraviolet rays, observation of biological activity at night, surveillance of military coastline at night, and the like.
(5), ultra-low illumination camera ultra-low illumination camera using EXVIEWHAD technology has greatly improved the sensitivity, its color illumination up to 0.05LUX, black and white is up to 0.003-0.001LUX. When equipped with a dedicated infrared device, high-resolution black-and-white images can be obtained, enabling 0Lux shooting.
Fourth, the camera control <br> <br> order to expand the scope of monitoring, surveillance cameras required to achieve rotation, zoom, magnification change, auto-focus. The realization of these functions requires the digital hard disk video recorder to control the camera through the controller.
1. Rotary control engineers use the PTZ to install and fix the camera. The PTZ is divided into fixed PTZ and electric PTZ. The fixed pan/tilt head is suitable for the case where the monitoring range is not large. After the camera is mounted on the fixed pan/tilt head, the horizontal and tilt angles of the camera are adjusted, and after the best working condition is reached, the adjustment mechanism can be locked. The stepper motor is installed on the electric gimbal. The motor receives the signal from the controller and drives the camera to rotate for accurate positioning. It is suitable for large-scale monitoring.
PTZ can be divided into a horizontal pan-tilt head that can only rotate left and right, and an all-around pan-tilt head that can both rotate left and right and rotate up and down, depending on the characteristics of its rotation. In general, the horizontal rotation angle is 0° to 350° and the vertical rotation angle is +90°. The horizontal rotation speed of the constant-speed gimbal is generally 3° to 10°/s, and the vertical speed is about 4°/s. The horizontal rotation speed of the variable-speed pan/tilt head is generally between 0° and 32°/s, and the vertical rotation speed is between 0° and 16°/s. In some high-speed camera systems, the pan-tilt speed is up to 480°/s and the vertical rotation speed is above 120°/s.
2, to achieve power zoom, zoom, autofocus (1) the so-called integrated camera is to make the lens, CCD chip, video processing circuit, power supply, chassis integration as a whole, you can achieve power zoom, zoom, auto focus function. The ability to quickly and accurately achieve autofocus is the key to evaluating the quality of an integrated camera. A good product can focus on one shot at a time, while a product with a poor quality will reciprocate back and forth when focused. It takes multiple shots to focus. The current integrated cameras have become the mainstream with 16, 18, 20, 22, 27, and 32 times zooming. The trend is that the illumination is getting lower and lower, and the optical multiple is getting higher and higher. Note that the zoom factor here is the optical zoom.
The key technologies of the integrated camera are lens, CCD and DSP processing modules. High-end lenses are mainly mastered by Japanese manufacturers such as Canon, Camputar, Avenir and others. CCD chip is mainly Sony of Japan, Sony CCD is divided into two types of SuperHAD and Exview, Exview is the latest technology, commonly used 1/4 inch size, higher noise ratio than SuperHAD; on DSP processing chip, Sony's DSP chip can be The color of the image is handled well so that the image looks very bright. Canon, Nikon's DSP is better at capturing light and focusing.
(2) Using a motorized zoom lens and an ordinary camera to combine a power zoom lens with an ordinary camera and use the principle of ordinary camera video drive to achieve automatic control of lens focal length, aperture, and focus. At present, some manufacturers have developed an ultra-high 60x motorized zoom lens "D60×12.5". Its focal length of 750mm (up to 1500mm with a zoom lens) clearly distinguishes people 3 kilometers away.
V. Network transmission of video images 1. Analog video camera + digital video recorder + computer network system This is currently the most widely used network video surveillance system. By setting ports, gateways, and routers, on-site digital hard disk recorders serve as servers at remote locations. With special monitoring software or plug-ins installed on the client's computer, users can see thousands of miles away from the Internet via the Internet, enabling single-channel, multi-channel video remote monitoring and recording.
2. Analog video camera + network video server + computer network system The analog camera output signal is an analog signal, the computer processing signal is a digital signal, and the network transmission is also a digital signal. The network video server (VideoServer) simulates the analog signal of the camera. It is converted into a digital signal, compressed and coded by an efficient compression chip, and the digital signal that can be transmitted in a computer network is transmitted in the form of a digital signal in a computer network. Therefore, the network video server can also be referred to as a Video Coder. When one end of the video server is connected with the analog camera's output signal, the other end is plugged into a computer network cable, and then a gateway, routing is set in any computer on the Internet, open IE browser, enter the IP address or domain name can be in the computer I saw the monitor screen. If the analog camera is equipped with a pan/tilt head, we can also use the computer to zoom, zoom, and rotate the camcorder. In the network video server also has to be embedded real-time operating system, can be Linux version, it can be Windows version, from the stability point of view, Linux version is superior. With the network video server, different cameras can be selected and equipped for more flexibility.
3. Network Camera + Computer Network System The network camera integrates the analog camera with the network video server. Built-in analog/digital conversion and video server functions inside the camera, like the network video server, realize network communication and data transmission according to the network protocol, and can also receive alarm signals and send out alarm signals. This is more convenient, as long as the network camera is installed, plug in the Internet can browse.
4. CDMA wireless network video surveillance system The transmission described above is wired transmission, but it is obviously very difficult to use wired transmission in moving vehicles (automobiles), remote mines, and mountains. We can use mature wireless communication technologies. The representative product here is China Unicom's mobile video. VISCOM CDMA wireless network video surveillance system is a convenient product that integrates CDMA data communication functions and digital video encoding functions. It compresses the camera image through the video compression coding module and transmits it to the CDMA network through the smart wireless communication terminal to realize the functions of video data exchange, transmission/reception, encryption/decryption, codec, and link control and maintenance. The system can transmit real-time dynamic images to the nearest Unicom communication network from the user. Real-time image information can be obtained from the console in the system through the Internet. The system integrates the advantages of CDMA network and Internet network, and carries out remote monitoring and management anytime, anywhere.
VI. Explanation of Common Technical Specifications 1. Resolution The resolution of an image simply refers to the number of points displayed in the vertical direction of the screen level and direction. For example, 1024×728, where “1024†indicates the number of points displayed on the screen in the horizontal direction, and “768†indicates the number of points displayed in the vertical direction. The higher the resolution, the clearer the image. The higher the resolution, the clearer the display of the image.
2. The resolution of the definition camera is represented by lines, which are divided into horizontal lines and vertical lines. In practical engineering applications, we often use the horizontal line as the evaluation index of the camera definition. The more lines, the higher the definition. The resolution of a commonly used black and white camera is generally 450-600, and the resolution of a color camera is generally 330-480. The larger the value, the clearer the image is. In a general monitoring situation, a camera with about 450 lines can satisfy the requirements. For medical and image processing and other special occasions, a 600-line camera can obtain clearer images.
3, automatic gain control (AGC)
In order to enable the camera to output standard video signals under different illumination conditions, automatic gain control (AutoGainControl) is introduced into the video processing circuit to achieve gain feedback control by detecting the average level value of the video signal. The camera with AGC function will improve the sensitivity in low illumination, but it will also amplify the interference signal and make the image appear cluttered.
4, backlight compensation (BLC)
When the camera is photographed in a backlit environment, a black image appears on the screen. However, the backlight environment is difficult to avoid in security. At this time, backlight compensation is required. When the backlight compensation function is introduced, if the camera detects that the video level in a region of the captured image is relatively low, the AGC circuit described above improves and enhances the video level in the region, and increases the amplitude of the output video signal, so that the entire image. Clear and bright. If the subject you want to see appears dim due to the bright background, you can set BLC to ON to compensate for the strong backlight.
5. Electronic shutter (EE/AI) switching At the rear of the camera, we often see the EE/AI switch. EE refers to the electronic shutter mode; AI refers to the automatic iris lens mode. The electronic shutter of the camera is generally set to an automatic electronic shutter mode. Through the electronic shutter method, the exposure time of the CCD image sensor is adjusted according to the intensity of the incident light to obtain a clear image. The time of the electronic shutter is 1/50-1/100000. Between seconds.
6. Signal-to-noise ratio refers to the ratio of signal level to clutter level. Clutter includes power supply clutter, random clutter, and single-frequency clutter. It is often expressed in decibels (dB). The higher the signal-to-noise ratio, the less clutter it produces and the higher the image signal quality. Signal to noise ratio must not be less than 48dB.
7, white balance (AWB)
1, the main parameters of the lens focal length (f): focal length is the distance between the lens and the photosensitive element, by changing the lens focal length, you can change the magnification of the lens, change the size of the captured image. When the object is far from the lens, we can use the following formula: Lens magnification, focal length/object distance. Increase the focal length of the lens, increase the magnification, can narrow the distance, the scope of the picture is small, the details of the vision can be seen more clearly; if the focal length of the lens is reduced, the magnification is reduced, the scope of the picture is enlarged, and See bigger scenes.
The main parameters of the lens field of view angle: In the actual project, we often use the horizontal field of view angle to reflect the shooting range of the screen. The larger the focal length f, the smaller the angle of view, and the smaller the range of the picture formed on the photosensitive element. Conversely, the smaller the focal length f, the larger the angle of view and the larger the range of the picture formed on the photosensitive element.
Aperture: The aperture is mounted on the rear of the lens. The larger the aperture is opened, the greater the amount of light that passes through the lens and the higher the image clarity. The smaller the aperture is opened, the smaller the amount of light that passes through the lens, and the sharper the image is. low. Usually expressed as F (light flux). F=focal length (f)/clear aperture. In the technical indicators of the camera, we can often see such parameters as 6mm/F1.4, which means that the focal length of the lens is 6mm, luminous flux is 1.4, then we can easily calculate the clear aperture of 4.29mm. In the case where the focal length f is the same, the smaller the F value and the larger the aperture, the greater the luminous flux reaching the CCD chip, and the better the lens.
2, the classification of the lens by the perspective of the size classification by aperture
Second, to improve the clarity of the image is to improve the camera's photosensitivity 1, the role of the photosensitive element Currently, the mainstream of the surveillance camera's photosensitive element using CCD components, in fact, is a photoelectric conversion element. Compared with previous CMOS sensor, CCD sensitivity is 3 to 10 times that of CMOS, so the CCD chip can receive more optical signals, converted into electrical signals, filtered and amplified by the video processing circuit to form the video signal output. . The stronger the received light signal, the greater the amplitude of the video signal. The video signal can be seen by connecting the video signal to the video input of a monitor or television. The only thing that improves the clarity of the image is to improve the camera's photosensitivity.
2. Configuration of lens and CCD sensor In Figure 1, we can see that the image formed on the CCD sensor is smaller than the original image. The dimensions of the imaging surface of the CCD chip are different, and the image size formed is also different.
CCD imaging size is commonly used 1/2 inch, 1/3 inch, CCD size specifications determine the camera's specifications.
Lens and CCD Sensor Configuration The CCD image size, which is the ratio of the camera frame width and height, is the same as the TV screen width and height ratio, which is usually 4:3. This ensures that the video image of the camera on the display is not distorted.
Lens specifications are also divided into 1/2 inch, 1/3 inch, etc., 1/2 inch lens can be used for 1/2 inch, 1/3 inch camera; 1/3 inch lens can only be used for 1/ A 3-inch camera cannot be used with a 1/2-inch camera because the 1/3-inch lens has a luminous flux of only 44% of the 1/2-inch lens's luminous flux and cannot meet the luminous flux requirements of a 1/2-inch camera.
The configuration of the focal length of the lens is still illustrated in Figure 1. Determining the appropriate focal length is an important factor in determining image quality. f=vD/Vf=hD/H. Where f represents the focal length, v represents the height of the CCD imaging dimension, V represents the height of the object being observed, h represents the width of the CCD imaging dimension, H represents the width of the object being observed, and D represents the distance from the object to the lens. Assume that a 1/3†CCD camera is used to observe the object to be measured with a width of 500 mm and a height of 400 mm. The focal point of the lens is 5000 mm from the object. It can be calculated by the formula: focal length f=4.8×5000/500≈48 mm or focal length f=3.6× 5000/400≈45mm.
Third, how to shoot in poor light conditions of the environment to clear image <br> <br> surveillance cameras can be requested in poor light conditions or even at night there is no light in the environment, but also to record clear images. In the indicator of the camera, we can often see the low illumination.
1. Illumination Concept The illuminance is a unit that measures the sensitivity of a camera and is expressed in Lux, which means that the camera can capture images under dim lighting conditions. The lower the value of Lux, indicates that the camera can take clear images under lower lighting conditions. We know that the nominal value of the video signal generated by the camera is 1v, and the standard value is 700mv. For example, if a lens with an aperture of F1.2 is used, the amplitude of the video signal output by the camera is the standard amplitude when the illuminance of the scene being shot is 0.02 Lux. The value of 700mv is 33%-50%. At this time, the minimum illumination of the camera is 0.02Lux/F1.2. The minimum illuminance of the test must pay attention to the aperture of the lens. The smaller the F value and the larger the aperture, the lower the illuminance required. Different apertures have different minimum illumination values.
2. Plan to achieve low illumination camera We know that CCD camera can be divided into color and black and white cameras. The minimum illumination of ordinary cameras is shown in the table below.
The minimum illuminance of ordinary cameras is visible light in the wavelength range of 380nm to 780nm. The wavelength of visible light is divided into red, orange, yellow, green, cyan, blue and violet from the longest to the shortest. The wavelength shorter than the violet light is called the ultraviolet light, and the wavelength is shorter than the infrared light. The long is called infrared light. The surface of the CCD sensor has a transparent UV-absorbing electrode, so the CCD cannot receive ultraviolet light. The CCD chip of an ordinary color camera has red, green, and blue filter bars, so the color camera cannot experience infrared light. However, the spectral range of ordinary CCD black-and-white cameras is very wide, and not only visible light but also infrared light can be felt.
Based on the above principles, engineers often use the following solutions to capture clear images in environments with poor lighting conditions.
(1) Ordinary low-intensity CCD black-and-white camera + infrared lamp Infrared radiation “lighting†is installed at the monitoring site to generate infrared light that cannot be seen by the human eye and can be captured by an ordinary camera. Night-time shooting can be achieved by a CCD black-and-white camera.
(2) Color to black and white video camera and infrared light The so-called color to black and white video camera refers to a daytime color camera. When the night lighting conditions are poor, the use of black and white images for high infrared sensitivity, automatically switches to black and white. Photographed with infrared rays. When combined with infrared light, the low-light camera must meet the minimum illumination supported by the infrared light.
(3) Infrared low-illumination color camera The infrared low-sensitivity color camera has an infrared sensitivity that is more than 4 times higher than that of a normal camera and can operate at zero illuminance (0 Lux).
Infrared low-illumination color camera (4) Low-speed shutter camera The low-speed shutter camera, also known as a screen-accumulating camera, continuously stores multiple frames (up to 128 frames) on a computer, resulting in poorly-lit and blurry pictures, and accumulates to become a clear picture. With SLOWSHUTTER technology, shooting under 0.008L/F1.2 illumination is achieved. This low-illuminance camera is suitable for museums that prohibit the destruction of red and ultraviolet rays, observation of biological activity at night, surveillance of military coastline at night, and the like.
(5), ultra-low illumination camera ultra-low illumination camera using EXVIEWHAD technology has greatly improved the sensitivity, its color illumination up to 0.05LUX, black and white is up to 0.003-0.001LUX. When equipped with a dedicated infrared device, high-resolution black-and-white images can be obtained, enabling 0Lux shooting.
Fourth, the camera control <br> <br> order to expand the scope of monitoring, surveillance cameras required to achieve rotation, zoom, magnification change, auto-focus. The realization of these functions requires the digital hard disk video recorder to control the camera through the controller.
1. Rotary control engineers use the PTZ to install and fix the camera. The PTZ is divided into fixed PTZ and electric PTZ. The fixed pan/tilt head is suitable for the case where the monitoring range is not large. After the camera is mounted on the fixed pan/tilt head, the horizontal and tilt angles of the camera are adjusted, and after the best working condition is reached, the adjustment mechanism can be locked. The stepper motor is installed on the electric gimbal. The motor receives the signal from the controller and drives the camera to rotate for accurate positioning. It is suitable for large-scale monitoring.
PTZ can be divided into a horizontal pan-tilt head that can only rotate left and right, and an all-around pan-tilt head that can both rotate left and right and rotate up and down, depending on the characteristics of its rotation. In general, the horizontal rotation angle is 0° to 350° and the vertical rotation angle is +90°. The horizontal rotation speed of the constant-speed gimbal is generally 3° to 10°/s, and the vertical speed is about 4°/s. The horizontal rotation speed of the variable-speed pan/tilt head is generally between 0° and 32°/s, and the vertical rotation speed is between 0° and 16°/s. In some high-speed camera systems, the pan-tilt speed is up to 480°/s and the vertical rotation speed is above 120°/s.
2, to achieve power zoom, zoom, autofocus (1) the so-called integrated camera is to make the lens, CCD chip, video processing circuit, power supply, chassis integration as a whole, you can achieve power zoom, zoom, auto focus function. The ability to quickly and accurately achieve autofocus is the key to evaluating the quality of an integrated camera. A good product can focus on one shot at a time, while a product with a poor quality will reciprocate back and forth when focused. It takes multiple shots to focus. The current integrated cameras have become the mainstream with 16, 18, 20, 22, 27, and 32 times zooming. The trend is that the illumination is getting lower and lower, and the optical multiple is getting higher and higher. Note that the zoom factor here is the optical zoom.
The key technologies of the integrated camera are lens, CCD and DSP processing modules. High-end lenses are mainly mastered by Japanese manufacturers such as Canon, Camputar, Avenir and others. CCD chip is mainly Sony of Japan, Sony CCD is divided into two types of SuperHAD and Exview, Exview is the latest technology, commonly used 1/4 inch size, higher noise ratio than SuperHAD; on DSP processing chip, Sony's DSP chip can be The color of the image is handled well so that the image looks very bright. Canon, Nikon's DSP is better at capturing light and focusing.
(2) Using a motorized zoom lens and an ordinary camera to combine a power zoom lens with an ordinary camera and use the principle of ordinary camera video drive to achieve automatic control of lens focal length, aperture, and focus. At present, some manufacturers have developed an ultra-high 60x motorized zoom lens "D60×12.5". Its focal length of 750mm (up to 1500mm with a zoom lens) clearly distinguishes people 3 kilometers away.
V. Network transmission of video images 1. Analog video camera + digital video recorder + computer network system This is currently the most widely used network video surveillance system. By setting ports, gateways, and routers, on-site digital hard disk recorders serve as servers at remote locations. With special monitoring software or plug-ins installed on the client's computer, users can see thousands of miles away from the Internet via the Internet, enabling single-channel, multi-channel video remote monitoring and recording.
2. Analog video camera + network video server + computer network system The analog camera output signal is an analog signal, the computer processing signal is a digital signal, and the network transmission is also a digital signal. The network video server (VideoServer) simulates the analog signal of the camera. It is converted into a digital signal, compressed and coded by an efficient compression chip, and the digital signal that can be transmitted in a computer network is transmitted in the form of a digital signal in a computer network. Therefore, the network video server can also be referred to as a Video Coder. When one end of the video server is connected with the analog camera's output signal, the other end is plugged into a computer network cable, and then a gateway, routing is set in any computer on the Internet, open IE browser, enter the IP address or domain name can be in the computer I saw the monitor screen. If the analog camera is equipped with a pan/tilt head, we can also use the computer to zoom, zoom, and rotate the camcorder. In the network video server also has to be embedded real-time operating system, can be Linux version, it can be Windows version, from the stability point of view, Linux version is superior. With the network video server, different cameras can be selected and equipped for more flexibility.
3. Network Camera + Computer Network System The network camera integrates the analog camera with the network video server. Built-in analog/digital conversion and video server functions inside the camera, like the network video server, realize network communication and data transmission according to the network protocol, and can also receive alarm signals and send out alarm signals. This is more convenient, as long as the network camera is installed, plug in the Internet can browse.
4. CDMA wireless network video surveillance system The transmission described above is wired transmission, but it is obviously very difficult to use wired transmission in moving vehicles (automobiles), remote mines, and mountains. We can use mature wireless communication technologies. The representative product here is China Unicom's mobile video. VISCOM CDMA wireless network video surveillance system is a convenient product that integrates CDMA data communication functions and digital video encoding functions. It compresses the camera image through the video compression coding module and transmits it to the CDMA network through the smart wireless communication terminal to realize the functions of video data exchange, transmission/reception, encryption/decryption, codec, and link control and maintenance. The system can transmit real-time dynamic images to the nearest Unicom communication network from the user. Real-time image information can be obtained from the console in the system through the Internet. The system integrates the advantages of CDMA network and Internet network, and carries out remote monitoring and management anytime, anywhere.
VI. Explanation of Common Technical Specifications 1. Resolution The resolution of an image simply refers to the number of points displayed in the vertical direction of the screen level and direction. For example, 1024×728, where “1024†indicates the number of points displayed on the screen in the horizontal direction, and “768†indicates the number of points displayed in the vertical direction. The higher the resolution, the clearer the image. The higher the resolution, the clearer the display of the image.
2. The resolution of the definition camera is represented by lines, which are divided into horizontal lines and vertical lines. In practical engineering applications, we often use the horizontal line as the evaluation index of the camera definition. The more lines, the higher the definition. The resolution of a commonly used black and white camera is generally 450-600, and the resolution of a color camera is generally 330-480. The larger the value, the clearer the image is. In a general monitoring situation, a camera with about 450 lines can satisfy the requirements. For medical and image processing and other special occasions, a 600-line camera can obtain clearer images.
3, automatic gain control (AGC)
In order to enable the camera to output standard video signals under different illumination conditions, automatic gain control (AutoGainControl) is introduced into the video processing circuit to achieve gain feedback control by detecting the average level value of the video signal. The camera with AGC function will improve the sensitivity in low illumination, but it will also amplify the interference signal and make the image appear cluttered.
4, backlight compensation (BLC)
When the camera is photographed in a backlit environment, a black image appears on the screen. However, the backlight environment is difficult to avoid in security. At this time, backlight compensation is required. When the backlight compensation function is introduced, if the camera detects that the video level in a region of the captured image is relatively low, the AGC circuit described above improves and enhances the video level in the region, and increases the amplitude of the output video signal, so that the entire image. Clear and bright. If the subject you want to see appears dim due to the bright background, you can set BLC to ON to compensate for the strong backlight.
5. Electronic shutter (EE/AI) switching At the rear of the camera, we often see the EE/AI switch. EE refers to the electronic shutter mode; AI refers to the automatic iris lens mode. The electronic shutter of the camera is generally set to an automatic electronic shutter mode. Through the electronic shutter method, the exposure time of the CCD image sensor is adjusted according to the intensity of the incident light to obtain a clear image. The time of the electronic shutter is 1/50-1/100000. Between seconds.
6. Signal-to-noise ratio refers to the ratio of signal level to clutter level. Clutter includes power supply clutter, random clutter, and single-frequency clutter. It is often expressed in decibels (dB). The higher the signal-to-noise ratio, the less clutter it produces and the higher the image signal quality. Signal to noise ratio must not be less than 48dB.
7, white balance (AWB)
We diviided the led light according to the using eviiroment. Most of our product is the commercial LED Lighting
Commercial lighting is a term used to describe lighting that is used in commercial spaces, including auto dealerships, distribution centers, churches, factories, offices, and warehouses. Unlike residential lighting, commercial lighting is made to withstand more abuse and has a longer lifespan.
While the focus of residential lighting is often on aesthetics, commercial lighting is task orientated. Commercial lighting systems are designed based on what the application is. For example, in an office-type setting, you may see task lighting, which illuminates specific areas where employees need concentrated light to be able to perform their jobs.
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