Basic knowledge of the hottest camera

Camera Basics

1. What is a CCD camera

ccd is the abbreviation of charge coupled device. It is a semiconductor imaging device, so it has the advantages of high sensitivity, strong light resistance, small distortion, small volume, long service life, anti vibration and so on

2. Working mode of CCD camera

the image of the subject is focused on the CCD chip through the lens. The CCD accumulates a corresponding proportion of charge according to the intensity of light. The charge accumulated by each pixel moves outward point by point under the control of video timing, and forms a video signal output after filtering and amplification. When the video signal is connected to the video input of the monitor or TV, you can see the same video image as the original image

3. Scanning system

according to the different frequencies of power supply in various countries, PS. Sundaram and his colleagues showed the difference between Al system and NTSC system using 3D printing to manufacture flat electronic composites with specific regional residual stress. 50Hz: color is PAL system, black and white is CCIR system, standard is 625 lines, 50 fields. 60Hz: the cutting edge or small round bar supported by color is in line contact with the surface of the sample. The color is NTSC system, black and white is EIA system, 525 lines, 60 fields. PAL system and CCIR system are adopted in China, and NTSC system and EIA system are adopted in Europe and America. Therefore, when selecting equipment, we must pay attention to the matching between equipment systems

3. Selection of resolution

the index for evaluating camera resolution is horizontal resolution, which is in line pairs, that is, the number of black-and-white line pairs that can be distinguished after imaging. The resolution of commonly used black-and-white cameras is generally, and the color is. The larger the value, the clearer the image. In general monitoring occasions, the requirements can be met with a black-and-white camera with about 400 lines. For special occasions such as medical treatment and image processing, a 600 line camera can get clearer images

4. Imaging sensitivity

usually indicates the camera sensitivity with the minimum environmental illumination requirements. The sensitivity of black-and-white cameras is about 0 5lux (Lux), color cameras are mostly more than 1Lux. 0.1Lux camera is used for ordinary monitoring occasions; It is recommended to use a 0.02Lux camera at night or when the ambient light is weak. When used with near-infrared lamps, low illumination cameras must also be used. In addition, the camera sensitivity is also related to the lens. 0.97lux/f0.75 is equivalent to 2.5lux/f1.2 is equivalent to 3.4lux/f1

reference ambient illumination:

100000lux in summer sunshine, 10000lux outdoors in cloudy days, 10000lux

1000lux in TV studio, 60W desk lamp, 60cm desktop, 300lux

indoor fluorescent lamp, 100lux in dusk, 10lux

20cm indoor candle lux night street lamp, 0.1lux

5 Electronic shutter

the time of the electronic shutter is between 1//100000 seconds. The electronic shutter of the camera is generally set to the automatic electronic shutter mode, which can automatically adjust the shutter time according to the brightness of the environment to get a clear image. Some cameras allow users to manually adjust the shutter time to adapt to some special applications

6. Scanning system

there are PAL system and NTSC system according to the different frequencies of power supply in various countries. 50Hz: PAL system, interlaced scanning system (black and white is CCIR), standard is 625 lines, 50 fields. 60Hz: NTSC system, 525 lines, 60 fields (black and white is EIA)

7. External synchronization and external trigger

external synchronization refers to that different video devices use the same synchronization signal to ensure the synchronization of video signals, which can ensure that the video signals output by different devices have the same start and end time of frames and lines. In order to realize external synchronization, it is necessary to input a composite synchronization signal (c-sync) or composite video signal to the camera. External synchronization does not guarantee that users can get a complete and continuous frame of image from the specified time. To achieve this function, some special cameras with external trigger function must be used

8. Spectral response characteristics

ccd device is made of silicon material, which is sensitive to near-infrared, and the spectral response can be extended to about 1.0um. Its response peak is green light (550nm), and the distribution curve is shown in the right figure. During covert monitoring at night, near-infrared lights can be used to illuminate, so human eyes can't see the environmental conditions clearly, but they can clearly image on the monitor. Because there is a layer of transparent electrode absorbing UV on the surface of CCD sensor, CCD is not sensitive to UV. There are red, green and blue filters on the imaging unit of the color camera, so the color camera is not sensitive to infrared and ultraviolet

9. The size of CCD chip

c the third kind belongs to the imaging size of cold inlaid packing CD. The commonly used imaging sizes are 1/2 ", 1/3", etc. the smaller the imaging size is, the smaller the volume of the camera can be made. Under the same optical lens, the larger the imaging size is, the larger the field angle is. Chip specification imaging surface size (width x height) diagonal 1/2 6.4x4.8mm 1/3 4 Semi automatic impact testing machine 8x3.6mm 6mm

10 Camera interface

ccd camera interface has two industrial standards, namely C interface and CS interface. The threaded parts of the two are the same, but the distance from the lens to the photosensitive surface is different

c mounting base: the distance from the lens mounting reference plane to the focus is 17.526mm

cs mounting base: the distance from the lens mounting datum plane to the focus is 12.5mm

11. assembly principle of camera and lens:

cs interface camera is equipped with CS interface lens

cs interface camera is equipped with C interface lens, and adapter ring is required between camera and lens

c interface camera is equipped with C interface lens

c interface camera does not need to be equipped with CS interface lens. (end)