Camera parameters professional explanation
Q: What is backlight compensation?
Backlight compensation can provide ideal exposure of the target in front of very strong background light, regardless of whether the main target moves to the middle, up, down, left or right, or anywhere on the screen.
An ordinary camera that does not have super dynamic characteristics only has a shutter speed of 1/60 seconds and F2.0 aperture selection, but a very bright background behind a main target or a point light source is inevitable and the camera will acquire The average of all recent rays determines the level of exposure. This is not a good idea because when the shutter speed increases, the aperture will be closed causing the main target to become too dark to be seen. To overcome this problem, a method called backlight compensation is widely used on most cameras through a weighted area theory. The image is first divided into 7 blocks or 6 areas (two areas are repeated). Each area can be individually weighted to calculate the exposure level. For example, the middle part can be added to the rest of the block by 9 times, so that one is in the middle of the screen. The goal of the location can be seen very clearly, because the exposure is mainly calculated with reference to the light level of the middle region. However, there is a very big flaw. If the main target moves from mid-to-left to the top, bottom, left and right positions of the screen, the target will become very dark, because now it is not differentiated and has not been weighted.
Q: What is Starlight mode?
Starlight mode allows the CCD camera to see clear color images under very low light conditions, such as a 0.0002Lux illumination level.
All CCD cameras are designed to operate at shutter speeds of 1/50, 1/60 to 1/2000 seconds, so the minimum illumination level or sensitivity is limited to 3 to 6 Lux using F1.2 and 5600k. The proprietary digital signal processor of the star mode CCD camera can make the shutter speed of the CCD as low as 1~10 seconds, because the physics of the long shutter opening, the CCD can collect more photons, so it is 100 to 600 times more than the traditional camera. The sensitivity.
Q: What is vertical synchronization, color video composite signal synchronization, external synchronization, DC line lock, and full synchronization?
This is a different synchronization method between cameras.
Lock-in is the best method for perfect synchronization between two precision applications such as broadcast studio cameras. It will be synchronized: horizontal, vertical, even/odd regions, color trigger frequency and phases.
Vertical synchronization is the easiest way to synchronize two cameras. The vertical drive frequency ensures that the video can use the old switching period or four-segment machine to display several image sources on the same monitor. The vertical drive signal is usually composed of pulses with a repetition rate of 20/16.7 ms (50/60 Hz) and a pulse width of 1 to 3 ms.
The color video composite signal represents video and color trigger signals, meaning that the camera can synchronize with an external composite color video signal. However, despite the so-called color video composite signal synchronization, only horizontal synchronization and vertical synchronization are actually performed without color trigger synchronization.
External synchronization is very similar to color video composite signal synchronization. A camera can be synchronized to the video signal of another camera. An external synchronization camera can use the input color video composite signal to extract horizontal and vertical synchronization signals for synchronization.
DC line locking is an old technology that uses a DC 50/60 Hz power line current to synchronize the camera. Because DC 24V power is widely used in most building fire alarm systems, it is very easy to obtain. Since old models of switchers and segmentation systems do not have digital memory functions, to maintain stable images, synchronization between cameras is very necessary. The DC line locking is the synchronization of the camera to AC 50/60 Hz, and the time correlation and level of the color channels. Unconstrained / vertical signals result in poor color conversion (color phase design), so all users using AC line locks inevitably lose their color conversion. Fortunately, today's splitters and 16-channel composite processors as well as hard disk recorders have internal memory to overcome this problem, eliminating the need for synchronization signals, so AC line locks may be eliminated several years later.
Q: What is the minimum extent of a CCD camera? Is it the limit of 11.5x50 mm or 22x23 mm?
The size of the CCD camera mainly depends on the four main components, the size of the CCD sensor, the digital signal processor, the CDS and the vertical drive. Because these chips must be fabricated with different semiconductor technologies, it is not possible to merge them into a single IC. The CCD sensor, as the main part, has been greatly reduced, from 2/3 inch to 1/2 inch to 1/3 inch to 1 /4 inch and 1/6 inch and 1/7 inch, however, the smaller the CCD size, the worse the rotation performance, so the 1/6 inch CCD is much worse than 1/4 inch, so the 1/4 inch CCD It has been the mainstream for many years. A 1/4-inch CCD has a 10x10 mm size as the main component, and the digital signal processor will be larger than the CCD if a 15x15 mm QFPGA package is used, further increasing the size of the camera's single board. Most companies today can only reduce the CCD camera board size to 44x44 mm.
Q: What is ultra-wide dynamic?
Ultra-wide dynamics is a feature that allows the camera to see images under very strong contrast.
A wide dynamic camera is more than a dozen times larger than a camera with a traditional 3:1 dynamic range. Natural light ranges from 120,000 Lux to 0.00035 Lux at night. When the camera looks out of the window from the room, the indoor illumination is 100 Lux, while the outside scenery may have an illumination of 10,000 Lux. The contrast is 10,000/100=100:1. This contrasting eye can be easily seen because the human eye can handle a contrast ratio of 1000:1. However, traditional closed-circuit surveillance cameras can deal with it with great problems. Traditional cameras have only a 3:1 contrast performance. Choose to use 1/60 seconds of electronic shutter to get the correct exposure of the indoor target, but the outdoor image will be erased (all white); or alternatively, the camera select 1/6000 second to get the perfect exposure of the outdoor image, but the indoor The image will be erased (full black). This is a long-standing defect since the camera was invented.
Q: What is a star camera?
Starlight CCD cameras have photons on the CCD sensor that are 2 to 128 times (1 to 2 seconds) longer than the maximum exposure time (1/60 or 1/50 second) of an ordinary CCD camera. As a result, the minimum illuminance at which the camera produces usable images is reduced by 2 to 128 times. Using a star camera with a frame-accumulation technique, users can see color images under the conditions of the illuminance of stars (0.0035 Lux), and see the black-and-white images under the cloudy illuminance conditions (0.0002 Lux), and the scattered background light in the city ( Such as light pollution) is sufficient to produce good color exposure.
Q: What is the peak induction mode?
The peak-sensing mode uses the average value of the image instead of the entire image to determine the exposure index. Users of the rule system can respond to the most demanding requirements, such as capturing a white point image in the dark and seeing the small light. White point details and colors.
Q: What is a CMOS camera? How is it different from a CCD camera?
A CMOS sensor is a sensor that is typically 10 times slower than a CCD sensor.
Because the human eye can see the target below 1Lux illumination (full moon night), the CCD sensor can usually see slightly better than 0.1 to 3 Lux for the human eye, which is 3 to 10 times the sensitivity of the CMOS sensor.
Monitoring System FAQ - Camera
1. No image output
a. Check if the power supply is connected and the power supply voltage is sufficient.
B. BNC connector or video cable is not in poor contact.
C. Is the lens aperture open?
D. Whether the video or DC driven auto iris lens control wire is connected.
2. Bad image quality
a. Whether the lens is fingerprinted or dirty.
B. Is the aperture adjusted?
C. Poor contact of the video cable.
D. There is no problem with the electronic shutter or white balance settings.
E. Is the transmission distance too far?
F. Voltage is normal.
G. Is there a source of interference nearby?
H. When installing in an elevator, ensure that the elevator is insulated from interference.
i. Is the CS interface connected?
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