How to choose a suitable lens surveillance camera Table for 1/3in lens Monitoring the angle of a shot, a proportion of the distance The relative aperture F- F F=f/D f= the number of aperture, focal length, aperture D= lens The focal length of the lens 2.8mm 3.5mm 4mm 4.8mm 6mm 8mm 1/3 "CCD from the angle of 86.3 ° 67.4 ° to 62 ° and 52.2 ° 42.3 ° 32.6 ° The distance of the object 4.3m 5.4m 6m 7.3m 9m 12m The focal length of the lens 12mm 16mm 25mm 60mm 73.8mm 1/3 "CCD from the angle of 22.1 ° 17.1 ° 10.6 ° 3.5 ° 2.9 ° The distance of the object 18mm 25mm 38mm 120mm 150mm In order to monitor display 5m objects shall prevail Lens mounting part diameter of 25.4mm Lens mounting datum to the focal distance of 17.526mm C type lens mounted to the camera CS interface to add 5mm connecting ring thickness The main difference is the size of the lens: Lens more look closer, but the visual range is wide; the lens more see farther, but the visual range is narrow. Our baby classification inside, dome camera can choose 3.6MM or 6MM lens; 30 meters waterproof infrared camera can choose 3.6MM, 6MM or 8MM lens; More than 30 meters waterproof infrared camera can choose 4MM, 6MM, 8MM, 12MM, 16MM, 25MM lens (lens. These are big CS lens all metal) Calculation method for monitoring the camera angle The 1/3 camera as an example: The best visual range (m) corresponding to the size of *2- = shot dead Note: the best visual range is dead outside the distance Such as: 12MM lens visual angle of 22 degrees, the visual distance the best is 24 meters (including dead distance), according to the formula: visual range of the best angle of 22 degrees, the visual range camera 4 meters to 24 meters The choice of lens: lens mm smaller numbers, more open field of vision, but look closer; lens mm higher numbers, vision and more narrow, but see the farther the distance, the two can not have it both ways) The calculation formula of camera lens Calculation formula: Department of field of view and the focal length of the calculated field refers to the uptake of object size, field size is the distance to the lens to be ingested objects, camera head and image size required to determine the. The focal length of the lens, field lens to be calculated as follows: the size and distance of uptake of objects: f=wL/W f=hL/h F: the focal length of the lens W: image width(object imaging width in the CCD target surface) W: object width L: object to camera distance H: image height (an image of an object in the CCD target surface height) field (uptake of scenes) height H: object height Because the camera screen width and height with the TV screen width and height, the ratio is 4:3, when the L invariant, H or W increases, f becomes smaller, when H or W unchanged, L increases, f increases. Calculation of angle of view If the horizontal or vertical angle can be calculated according to the formula of the width and height. Horizontal view angle β (horizontal viewing angle) β =2tg-1= vertical field of view angle Q (vertical viewing angle) q=2tg-1= type W, H, f. Horizontal view angle and the vertical angle of view as follows: q= or =q listed in Table 2 value B the horizontal view of different sizes and different focal length camera layer of f angle, if the horizontal or vertical angle can be calculated from the field angle can be calculated out of the field H and field width W. height H=2Ltg, W=2Ltg for example; camera tube is 17mm (2/3in), the focal length of the lens f to 12mm, from table 2 check horizontal viewing angle of 40 degrees. Lens and ingested objects at a distance of 2m, find the field width W. W=2Ltg=2 * 2tg=1.46m H=W= * 1.46=1.059m f more and long focal length, field of view angle is small, the goal of surveillance is small. The graphic method As previously shown, the camera field of view by the wide (W). High (H) and the distances from the camera (L) decision, once the decision to the camera to monitor the scene, the correct choice of the focal length of the lens on the origin of 3 factors; * to monitor the dimension of the object * the camera and the object distance * camera imager ruler: 1/3 ", 1/2" 2/3 ", or 1" Graphic lens selection steps: there is a simple relationship between field of view and the focal length of the lens required. Using this relation can choose appropriate lens. Maximum width estimated or measured field; estimation or measurement camera and photographed the scene and the distance between the lens; use 1/3 "used in Figure 2, the use of 1/2 lens used in Figure 3, the use of 2/3" lens use figure 4, using a 1 lens use figure 5. Method: on the icon to W and L axes 2-5, find out the focal length of the lens should be used. To ensure that the object is completely contained in the field, should choose the coordinate intersection, numerical surface that line indicator. For example: wide field of view 50m, distance of 40m, using the 1/3 "format of the lens, at the intersection graphs of 4mm lens than partial line a bit. This shows that if you use the 4mm lens can not cover the 50m field of view. And with a 2.8mm lens can completely cover the field. f=vD/V f=hD/H Wherein, f represents the focal length, V represents the vertical CCD target surface height, V represents the observed object height, H represents the level of CCD target surface width, H represents the observed object width. Give an example:If 1/2 "CCD camera observation, the object to be measured 440 mm wide, 330 mm high, lens focal distance of 2500 mm objects. Can be calculated by formula:Focal length f=6.4X2500/440 = 36 mm or 36 mm focal length is f=4.8X2500/330 When the focal length is numerical calculated, if there is no corresponding to the focal length of the lens is very normal, then according to the catalogue choice of similar models, the general selection value smaller than the calculation, this view will be greater. In order to obtain the same point of view from the 1/3 "and 1/2" 1/3 "CCD CCD camera, camera lens focal length must be reduced; if the same focal length in 1/3" CCD and 1/2 "CCD camera lens, the situation and how? 1/3" CCD camera than 1/2 "CCD camera is decreased obviously, at the same time image 1/3 ″ CCD camera, image on the monitor than 1/2 ″ CCD amplification, produced using the telephoto lens effect. In addition we select the lens should pay attention to such a principle: small size target surface CCD can use large size target surface CCD cameras, not vice versa. The reason is: if 1/2 "CCD by 1/3" camera lens, the light becomes smaller, the color will become worse, even image will defect; on the contrary, the amount of light will become large, the color will change, image effects will certainly be better. Of course, integrated a variety of factors, the camera or to choose the best matching lens.