Main function control of the hottest CCD camera

Main function control of CCD camera

1 Selection of synchronization mode

for a single CCD camera, the main synchronization modes are: internal synchronization, external synchronization, power synchronization and so on. Its specific functions are as follows:

□ internal synchronization: use the synchronization signal generated by the camera's built-in synchronization signal generation circuit to complete the synchronization signal control

□ external synchronization: the specific synchronization signal is sent to the external synchronization input of the camera through the external synchronization signal generator to meet the special control needs of the camera

□ power synchronization (linear lock): complete vertical synchronization with the AC power supply of the camera

for the image acquisition system composed of multiple CCD cameras, it is expected that all video input signals are vertically synchronized to avoid image distortion when changing the output of the camera. At this time, the synchronous signal generated by the same external synchronous signal generator can be used to drive multiple cameras to realize synchronous image acquisition of multiple cameras

2. Automatic gain control

ccd cameras usually have a video amplifier that amplifies the CCD signal, and its magnification is called gain. If the gain of the amplifier remains unchanged, the video signal will be saturated in a high brightness environment. Using the automatic gain control (AGC) circuit of the camera, the gain of the amplifier can be automatically adjusted with the change of illumination inside and outside the environment, so that the camera can work in a large illumination range

3. Backlight compensation

generally, the AGC working point of CCD camera is determined by the average value of the signal of the whole field of view. Dangshi 6 Vibration table (including impact table and collision table); When the field contains a bright background area and a dark foreground target, the determined AGC operating point is not completely suitable for the foreground target. When the background light compensation is started, the CCD camera only averages the sub area where the foreground target is located to determine its AGC working point, so as to improve the imaging quality

4. Electronic shutter

ccd cameras generally have the characteristics of electronic shutter, which does not need any mechanical parts. CCD camera adopts electronic shutter to control the accumulation time of CCD. When the electronic shutter is opened, the CCD camera outputs only the photocharge signal when the electronic shutter is opened, and the remaining photocharge signal is discharged. At present, the shortest electronic shutter time of CCD camera is generally 1/10000 second; When the electronic shutter is closed, the CCD accumulation time of NTSC camera is 1/60 second; For PAL camera, it is 1/50 second

a higher shutter speed will produce a "pause action" effect for observing moving images, which greatly increases the dynamic resolution of the camera. At the same time, when the electronic shutter speed increases, the luminous flux focused on the CCD decreases within the CCD integration time, which will reduce the sensitivity of the camera

5. γ (gamma) correction

in the whole vision system, two transformations are required: CCD sensor converts optical images into electrical signals, that is, the so-called photoelectric conversion; After the electrical signal is transmitted, the electrical signal is restored to an optical image by the display device at the receiving end, which is called electro-optical conversion. In order to make the image reproduced at the receiving end consistent with the original image at the output end, it is necessary to ensure that the comprehensive characteristics in the two transformations have linear characteristics

the relationship between the light (L) on the CCD sensor and the signal voltage (V) from the camera is v=l γ。 In a standard TV system, the camera's γ The coefficient is 0.45. For machine vision applications, γ The coefficient should be 1.0, thus providing a linear relationship between light and voltage

6. White balance

the white balance function is only used for D camera, the publisher of color CC products. Its main function is to realize the accurate reflection of the camera image to the actual scene. It is generally divided into manual white balance and automatic white balance

1 some artists have long been tired of traditional means. The automatic white balance function of CCD camera is generally divided into continuous mode and button mode. In continuous mode, the white balance setting of the camera will be continuously adjusted with the change of the color temperature of the scene, and the range is generally 2800~6000k. This method is suitable for occasions where the color temperature of the scene changes constantly during imaging, and can make the color performance more natural. However, when there is little or no white in the scene, the continuous white balance function cannot produce the best color effect; When in button mode, you can first aim the camera at the white target, then set the automatic mode switch and keep it in this position for a few seconds or until the image turns white. After performing white balance, reset the automatic mode switch to lock the white balance setting. At this time, the white balance setting will be stored in the memory of the camera, and its range is generally 2300~10000k. It is the most accurate and feasible to set the white balance in the way of buttons, which is suitable for most applications

when the CCD camera is in the manual white balance state, the red or blue color of the image can be changed manually, which promotes the in-depth cooperation between Dongqing and these enterprises in the fields of air chemical industry, electronic technology, commercial aircraft and so on. There are as many as 107 levels for adjustment. Such as increasing or decreasing red by one level, increasing or decreasing blue by one level, etc. (end)