| Security camera |
| Security camera 1. The types of lens (classification according to the applications) Wide-angle lens: Angle of 90 degrees of above, observation range is bigger, near image deformation. • standard lens: the Angle of 30 degrees or so, with wider range of use. Telephoto lenses: within 20 degrees Angle, focal length is few millimeters or hundreds of mm. Zoom lens: the lens focal length continuous variable, the focal length can be from wide Angle to telephoto, the greater the focal length, the more grown up like. Pinhole lens: used for covert observation, are often installed in places such as ceiling or wall. 2. Is the size of the object, the relationship between distance and focal length Set the height and width of the object to be taken respectively, H, W, D is the distance between the object and the lens of, the focal length of the lens for f.The height and width of the target surface imaging h, w, respectively, the computation formula is as follows: f = h * D/h = f w * D/w According to the above formula, is also easy to calculate the Angle of view, the following table for the target surface dimension and imaging target surface size table size 1 1/2 "1/3" h "2/3" 9.6 mm to 6.6 mm to 4.8 mm to 3.6 mm w 12.8 mm to 8.8 mm to 6.4 mm to 4.8 mm 3. The relative aperture In order to control the size of the luminous flux through the lens, are set up at the back of their lens aperture.Assumes that effective aperture of aperture for d, because of the light refraction, the actual effective aperture is d, bigger than d, d is defined as relative aperture and focal length f A, namely A = d/f, intensity of illumination with the relative aperture of lens decided by camera, as the intensity of illumination and is proportional to the square of the relative aperture of lens, commonly used in f = f/d, the reciprocal of the relative optical path to represent the size of the lens aperture.F value is smaller, the larger the aperture, the luminous flux reach CCD chip.So the focal length f equal, the smaller the f value, said lens, the better. 4. The focal length of lens 1) fixed focal length: fixed focal length, can be divided into two kinds of, with and without aperture aperture. • have aperture: the size of the lens aperture can be adjusted.According to the variation of environmental light, should be appropriate to adjust the size of the aperture.The size of the aperture can be manual or automatic adjustment.Artificial manual adjusting aperture, referred to as the aperture manually;Automatically adjust aperture lens with the micro motor, called automatic aperture. • no aperture: set the aperture, the light is fixed.Mainly with a constant light source or camera bring electronic shutter. 2) zoom: the focal length can be adjusted according to need, to be enlarged or reduced image of the object. Commonly used for six times, ten times zoom zoom lens. Three variable lens: adjustable focus, focus, adjustable aperture. Two variable lens: adjustable focal length, automatic tuning focus, aperture. 5. The principle of matching lens In order to get the expected effect of a camera, equipped with cameras, attention should be paid six basic elements: A) the size of the object to be taken B) are the details of the object size C) object distance D) the focal length E) the CCD camera on the surface of the target size F) the lens and the resolution of the camera system Note: Zoom lens, the positioning of the focal plane, and can adjust the optical system of continuously focal road.Zoom is by moving the lens inside the lens, changing the relative position between them.So you can change the focal length of the lens length within a certain scope and perspectives. The focal length, lens center or the second principal plane to the image gathering place.Unit is commonly mm or inches. Aperture - part within the camera lens, can adjust the optical mechanical diaphragm, also can be used to control the light through the lens of how many. Auto iris, lens diaphragm within the device, according to the video signal of television cameras adjust themselves, to adapt to the change of light intensity.Aperture diaphragm by opening or closing the aperture to control the transmission of light through a lens.Typical of the compensation range is 10000-1 to 300000-1. |
