When purchasing a surveillance camera, you can always see parameters such as CCD, horizontal resolution, and some features in the technical parameters. Understanding these parameters will give us a lot of help when choosing a camera.
1. What is a CCD camera?
CCD is the abbreviation of Charge Coupled Device (CCD). It is a kind of semiconductor imaging device and therefore has the advantages of high sensitivity, strong light resistance, small distortion, small size, long life, and shock resistance.
2. How the CCD camera works
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 light intensity. The charge accumulated by each pixel moves outward point by point under the control of the video timing, and is filtered and amplified to form an image. Video signal output. The video signal is connected to the video input of a monitor or television to see the same video image as the original image.
3. The choice of resolution
The index for evaluating the camera resolution is the horizontal resolution. The unit is the line pair, which 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 380-600, and the color is 380-480. The larger the value, the clearer the imaging. For general surveillance applications, a 400-line black-and-white camera can meet the requirements. For special occasions such as medical treatment and image processing, a 600-line camera can obtain clearer images.
4. Signal to noise ratio
That is, the ratio of the image signal of the camera to the noise voltage, the typical value of the CCD camera is between 45-55 dB, and the higher the signal-to-noise ratio, the better.
5. Imaging sensitivity
The sensitivity of the camera is usually indicated by the minimum ambient illumination requirement. The sensitivity of the black and white camera is approximately 0.02-0.5 Lux, and the color camera is more than 1 Lux. The 0.1Lux camera is used for ordinary surveillance applications; when used at night or when the ambient light is weak, a 0.02Lux camera is recommended. When used with near-infrared lamps, low-light cameras must also be used. In addition the sensitivity of the camera is also related to the lens, 0.97Lux/F0.75 is equivalent to 2.5Lux/F1.2 is equivalent to 3.4Lux/F1.4. Reference environment illumination: 100000Lux in summer sunshine, 10000Lux in cloudy outdoor, 1000Lux in TV studio, 60L tabletop 60Lux from 60W lamp, 100Lux in indoor light, 10Lux in evening room, 10-15Lux at 20cm, and 0.1L at night
6. Electronic shutter
The electronic shutter time is between 1/50-1/100000 seconds. The electronic shutter of the camera is generally set to the automatic electronic shutter mode. The shutter time can be automatically adjusted according to the brightness and darkness of the environment to obtain a clear image. Some cameras allow the user to manually adjust the shutter time to suit certain special applications.
7. External synchronization and external trigger
External synchronization refers to the use of the same synchronization signal between different video devices to ensure the synchronization of video signals. It can ensure that the video signals output by different devices have the same frame and line start and end times. In order to achieve external synchronization, a composite sync signal (C-sync) or composite video signal needs to be input to the camera. External synchronization does not guarantee that the user can obtain a complete continuous frame of images from a specified moment. To achieve this function, special cameras with external triggering must be used.
8. Spectral response characteristics
The CCD device is made of silicon and is sensitive to near-infrared. The spectral response can be extended to about 1.0um. The response peak is green (550 nm) and the distribution curve is shown on the right. When surveillance is performed at night during covert surveillance, near-infrared illumination can be used. The human eye can't see the environment, but it can be clearly imaged on the monitor. Since the surface of the CCD sensor has a transparent UV-absorbing electrode, the CCD is insensitive to ultraviolet light. There are red, green and blue filter strips on the imaging unit of the color camera, so the color camera is insensitive to infrared and ultraviolet.
9. CCD chip size
The image size of the CCD is usually 1/2", 1/3", etc. The smaller the image size, the smaller the camera size can be. In the same optical lens, the larger the imaging size, the larger the angle of view. Chip size Imaging surface size (width X height) Diagonal line 1/26.4x4.8mm8mm1/34.8x3.6mm6mm
The camera's angle of view is inseparable from the millimeter of the lens and the size of the CCD.
1. What is a CCD camera?
CCD is the abbreviation of Charge Coupled Device (CCD). It is a kind of semiconductor imaging device and therefore has the advantages of high sensitivity, strong light resistance, small distortion, small size, long life, and shock resistance.
2. How the CCD camera works
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 light intensity. The charge accumulated by each pixel moves outward point by point under the control of the video timing, and is filtered and amplified to form an image. Video signal output. The video signal is connected to the video input of a monitor or television to see the same video image as the original image.
3. The choice of resolution
The index for evaluating the camera resolution is the horizontal resolution. The unit is the line pair, which 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 380-600, and the color is 380-480. The larger the value, the clearer the imaging. For general surveillance applications, a 400-line black-and-white camera can meet the requirements. For special occasions such as medical treatment and image processing, a 600-line camera can obtain clearer images.
4. Signal to noise ratio
That is, the ratio of the image signal of the camera to the noise voltage, the typical value of the CCD camera is between 45-55 dB, and the higher the signal-to-noise ratio, the better.
5. Imaging sensitivity
The sensitivity of the camera is usually indicated by the minimum ambient illumination requirement. The sensitivity of the black and white camera is approximately 0.02-0.5 Lux, and the color camera is more than 1 Lux. The 0.1Lux camera is used for ordinary surveillance applications; when used at night or when the ambient light is weak, a 0.02Lux camera is recommended. When used with near-infrared lamps, low-light cameras must also be used. In addition the sensitivity of the camera is also related to the lens, 0.97Lux/F0.75 is equivalent to 2.5Lux/F1.2 is equivalent to 3.4Lux/F1.4. Reference environment illumination: 100000Lux in summer sunshine, 10000Lux in cloudy outdoor, 1000Lux in TV studio, 60L tabletop 60Lux from 60W lamp, 100Lux in indoor light, 10Lux in evening room, 10-15Lux at 20cm, and 0.1L at night
6. Electronic shutter
The electronic shutter time is between 1/50-1/100000 seconds. The electronic shutter of the camera is generally set to the automatic electronic shutter mode. The shutter time can be automatically adjusted according to the brightness and darkness of the environment to obtain a clear image. Some cameras allow the user to manually adjust the shutter time to suit certain special applications.
7. External synchronization and external trigger
External synchronization refers to the use of the same synchronization signal between different video devices to ensure the synchronization of video signals. It can ensure that the video signals output by different devices have the same frame and line start and end times. In order to achieve external synchronization, a composite sync signal (C-sync) or composite video signal needs to be input to the camera. External synchronization does not guarantee that the user can obtain a complete continuous frame of images from a specified moment. To achieve this function, special cameras with external triggering must be used.
8. Spectral response characteristics
The CCD device is made of silicon and is sensitive to near-infrared. The spectral response can be extended to about 1.0um. The response peak is green (550 nm) and the distribution curve is shown on the right. When surveillance is performed at night during covert surveillance, near-infrared illumination can be used. The human eye can't see the environment, but it can be clearly imaged on the monitor. Since the surface of the CCD sensor has a transparent UV-absorbing electrode, the CCD is insensitive to ultraviolet light. There are red, green and blue filter strips on the imaging unit of the color camera, so the color camera is insensitive to infrared and ultraviolet.
9. CCD chip size
The image size of the CCD is usually 1/2", 1/3", etc. The smaller the image size, the smaller the camera size can be. In the same optical lens, the larger the imaging size, the larger the angle of view. Chip size Imaging surface size (width X height) Diagonal line 1/26.4x4.8mm8mm1/34.8x3.6mm6mm
The camera's angle of view is inseparable from the millimeter of the lens and the size of the CCD.
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