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High-speed electronic shutter
High-speed electronic shutter allows the camera to clearly capture high-speed moving objects. Ordinary cameras can cause smearing when shooting high-speed or fast-moving objects. This is because the speed of the electronic shutter of ordinary cameras is not fast enough, that is, the CCD exposure time is too long in one cycle, and the accumulated charge on the CCD is controlled under the control of the DSP. During this time, the different sensitometric positions of the object on the CCD have become like images, so the picture we see is an object that is blurred and accompanied by tailing. How to avoid the tailing phenomenon? After understanding the causes of tailing, we are very clear that as long as the speed of the electronic shutter of the camera is fast enough, so that the CCD's light-sensitive time in each cycle (note that the cycle is not Change, still 1/50 second), the object will only be sensitive to a position in the CCD, then the output of this frame of the image, the object will be imaged in a position, if the actual CCD sensor time in each imaging cycle are It is so short, then the motion of the object is clear on the continuous screen of the output. In general, as long as the frame rate per second reaches 15 or more, the feeling of the image is continuous. Generally, the frame rate of the PAL system is 25, so the continuity of the image can be guaranteed. When it comes to real life, we can often see footage of bullets or missiles flying on television. The shooting of these images is the use of high-speed cameras. The bullet's flight path is quite clear and the camera's high-speed shuttering plays an important role.
Light supplement
The acceleration of the electronic shutter speed has led to a significant reduction in the CCD sensor time. The result is a serious shortage of charge accumulation, resulting in dark screens. This is almost an irreconcilable contradiction. If it is to be solved, only light compensation methods can be used. This is the principle of the mouth.
The camera used in the traffic bayonet has a high-speed electronic shutter function. This function ensures that when shooting high-speed vehicles, because the electronic shutter speed is fast enough, the vehicle is only imaged in one position of the CCD at each time, so the trajectory of the vehicle is clear. However, it is relatively dim. At the same time, when the electromagnetic coil on the local side feels that the vehicle is speeding, it feeds this signal back to the fill light. The fill light instantly lights up. The CCD receives a large amount of reflection from the object within the allowable light-sensing time. The number of charge increases rapidly. The license plate is clearly visible in the frame where the fill light is on. This is why we can often see some lights flickering at the intersection. Of course, the fill light can be completely flashed. The software control of the control terminal can fill the light when the vehicle is not speeding, and take a bright and clear picture of the vehicle whenever it is needed.
Therefore, when shooting a high-speed or fast-moving object, a high-speed electronic shutter camera is generally preferred, which can clearly show the motion of the object, and is very suitable for shooting a person to run or a vehicle traveling picture.
Automatic iris effect
Automatic electronic shutter can also achieve the effect of automatic aperture, if the aperture is relatively small, automatic electronic shutter will automatically adjust to the slow state, increase the CCD exposure time to increase the brightness of the screen, but inevitably cause image smear phenomenon Corresponding if the aperture is too large, too much light, resulting in a very bright picture, then the automatic electronic shutter will automatically adjust to a fast state, reduce the actual CCD exposure time, reduce the charge accumulation on the CCD, balance the screen brightness.
Wide dynamic camera
Currently, mature wide dynamic cameras in the market generally use the CCD for imaging twice or more times. When the contrast is strong, the camera first uses the normal shutter speed to expose the scene. At this time, because the normal shutter speed is slow, dark objects in the picture will be normally imaged, but due to the longer exposure time, the bright objects in the scene will appear brighter, and then the camera will be exposed again with a faster shutter speed. CCD sensation time is insufficient, and the imaging of bright objects is more appropriate, but the darker objects in the original scene will be darker. With the help of the DSP function of the camera, the two sub-screens will be cut and combined to form a light and dark scene in the original scene. All parts of the object brightness are more appropriate image output.
Because the wide dynamic camera inevitably uses the electronic shutter with normal speed, it will cause smearing when shooting fast objects. Therefore, it is not suitable for use as a traffic bayonet camera, and is only suitable for applications such as the entrance of a residential area. On occasion, the speed of the vehicle is not fast, and at the same time, due to the contrast between the brightness of the night lights and the license plate, this is precisely the suitable application of the wide dynamic camera.
For the interlaced scanning system, each complete picture is composed of two odd-numbered fields and two even-numbered fields. That is, there are 25 odd-numbered fields and 25 even-numbered fields per second, that is, 50. On the screen, each CCD will accumulate charge. If the charge transfer process can be suspended for a few fields, the charge inside the photoreceptor can be temporarily stored until a certain scene is exposed to light for many times before the charge transfer occurs. Accumulation of a large number of charges will undoubtedly increase the signal intensity and thus increase the brightness of the screen. However, the consequence of this is that the frame rate of the camera is reduced, resulting in dropped frames. Therefore, this type of multi-field accumulation of charges increases the market. Illumination cameras are usually only suitable for monitoring still or non-motion scenes, so that even if dropped frames are not visible.