With the advancement of technology and the improvement of living standards, the projector has entered our lives. The lens can be said to be an extremely important part of the projector, so let’s take a look at the projector lens together.
For the lens, in addition to the difference in quality, the key parameter is the size of the aperture f-number, f is the light transmission rate of the lens. The larger the aperture f (the smaller the f-number), the greater the light transmittance of the lens. The aperture of the projector lens is expressed by a numerical value, generally from 1.6 to 4.0. The large aperture of each lens is marked in front of the lens with a numerical value. What I want to explain here is that the f-number of the lens can reach 1.0 in an ideal state. Due to the constraints of manufacturing technology and price factors, the f-number can never be 1.0.
For the projector, the lens is a link in the optical path of the projector. The quality of the lens and whether the aperture value can be made small is directly related to the brightness. The size of the aperture is inversely proportional to the f-number. The smaller the aperture, the larger the aperture. The brightness of the projected image is high. For a fixed focus lens, the aperture value is a constant value. For a zoom lens, through the definition of the f value (the f value can be simply understood as the ratio of the focal length of the lens to the diameter of the optical lens). It can be seen that due to the change of focal length, its value is within a range. For example, f2.8-f3.4. The aperture value of the projector is a very important parameter. For example, if the same machine uses lenses with different f-numbers, the difference in brightness is very big! For example, an f2.8 projector is twice the brightness of the f4 projector, four times the brightness of the f5.6 projector, and eight times the brightness of the f8 projector…any two lenses, as long as their f-values are the same , Then the amount of light they transmit is exactly the same. For example, if two different lenses are both f/2.8, then the same amount of light will pass through the lens to the screen. It is not necessary that the projector lens is large, its f-number is large, and it is closely related to the focal length of the lens! It is possible that the f-number of a small-caliber projector lens is smaller than the f-number of a large lens (the amount of light passing is greater).
Focal length F
The focal length F is also expressed by a numerical value, usually from 50-210, divided into short focal length, standard focal length and long focal length, as well as ultra short focal length and super long focal length. The smaller the value, the shorter the focal length, the larger the value, the longer the focal length. The projector’s requirements for the lens focal length are generally 50-140 for the front projection, and the rear projection is generally about 35. The focal length determines the size of the projector and the screen when the predetermined size is full. Distance, the shorter the focal length, the closer the distance between the projector and the screen, and vice versa. If you want to project a large picture at a short distance, you need to choose a projector with a short focal lens, otherwise you need to choose a telephoto lens. General projectors are standard lenses.
How to choose a suitable F-number lens in actual use
The focal length of the lens determines the size of the image that the lens can form when the distance between the projector and the screen is certain. Then the shorter the focal length of the lens, the larger the image projected on the screen.
In the choice of the projector, in general application places, at the same price, the standard lens should be selected first. The standard lens is excellent in the color reproduction of the projected image and the geometric distortion of the image! For a small application space, if you want a large-size projected image, you should give priority to the use of a short-focus lens. (Of course, if conditions permit, you can also consider the method of using optical path refraction on a standard lens projector to obtain a large-size projected image. .) For large applications, when funds are abundant, the telephoto lens is given priority, because this installation method has many advantages. First of all, the influence of the projector fan noise on the viewer is well suppressed. , Secondly, in the viewer’s influence on the projector (smoker’s soot, diners’ food scraps, hot drink steam) factors, the influence of the telephoto projector is small! This also creates a comfortable working environment for the projector, which is convenient for the long-life operation of the projector.
For the aperture value, there is currently no room for choice. When choosing a projector, by comparing the aperture value of different projectors, you can know the power utilization rate of the projector product you have determined. For different aperture values, the brightness is the same. For projector products with small aperture (large aperture), the power of the lamp must be less than that of projector products with large aperture. Its significance lies in energy saving and consumption reduction.