Choosing lens for video surveillance camera
Lens is the eye of the camera, the quality of lens determined the clearance of images. Except focusing on the selection and design of CCD and DSP circuit, choosing an appropriate lens for security camera is very important to achieve the full features of security camera. Lens consist of one series or muti-series of optical lens, adopts the mechanical structure to form image. Different optical lens combination can form different distance of image. Manufacturers design and manufacture different camera lens to meet the various demands from market. Due to the complex of installation environment, some of security camera installer and security dealer may face problem on the selection of correct camera lens for video surveillance camera. We herein share some information with our own experience.
Types of camera lens for video surveillance camera.
Because the camera lens for video surveillance camera is one of important component, before any layout of video surveillance project, we should be very familiar with types of camera lens. Understand types and features for these camera lens, then we can use them appropriately. Now, camera lens with following ten types:
Fixed iris lens: With fixed focal length and fixed iris aperture, are widely used for place with the stable light conditions.
Manual iris lens: With fixed focal length, but Iris aperture adjusted manually to give the optimum camera image quality.
Auto iris lens (DC-drive): fixed focus, adopts DC voltage to adjust the iris aperture according to the light condition.
Auto iris lens (Video-drive): fixed focus, adopts video signal to adjust the iris aperture according to the light condition.
Manual iris zoom lens: Used for the indoor places with changes of light condition and view angle and distance.
Auto iris zoom lens: Used for the outdoor places with changes of light condition and view angle and distance.
Board lens: Widely used for Infrared Camera, indoor and outdoor.
Fisheye Lens: Used for the indoor places with changes of light condition and view angle and distance.
Motorized Zoom Lens: Remote control of zoom and focus axis. Mainly used for the indoor and outdoor place in different light condition, and various of depth of field.
Pin-hole lens: Mainly used for the spy surveillance and some special places.
CCTV Camera Lens Calculations Formula
There are many formulas for the calculations of object distance for camera lens, now we introduce the simple one among them. We herein provide below informaiton only for reference purpose.
1. Formula Calculation Method: View size and focal length calculation. View size means the size of object, The size of view depends on the distance of camera lens between object, lens focus and in order to generate an image of size on the film.
2. Camera lens view size and distance of object as below:
Basic formula: f=wL/W Another inverse: f=hL/H;
f: focal length (mm)
Lower case w: Width of image ( generate an image of width on CCD mm)
Capital W: Width of real object;
L: Distance between camera lens and object;
Lower case h: Height of image (generate an image of height on CCD)
H: Height of real object