Lens is the second element that affects the image quality of camera module after CMOS chip. Its composition is lens structure, which is composed of several lenses, which can generally be divided into plastic lens or glass lens. Of course, the so-called plastic lens is not pure plastic, but resin lens. Of course, its optical indicators such as light transmittance and photosensitivity are not comparable to coated lenses.
Generally, the lens structure for camera module includes:
1p, 2p, 1g1p, 1g2p, 2g2p, 2g3p, 4G, 5g, etc. The more lenses, the higher the cost, the better the relative imaging effect of the camera module; Glass lenses are more expensive than resin. Therefore, a high-quality HD camera module should use multi-layer glass lens! In order to reduce the cost, most camera modules in the market generally use ordinary plastic lenses or one glass one plastic lens (i.e. 1p, 2p, 1g1p, 1g2p, etc.), which has a great impact on the imaging quality!
The lens is composed of lens, filter device and lens barrel. There are three lens parameters, namely focal length f ', relative aperture d/f' and field angle 2 ω。
Lens focal length is an important index of camera module, which determines the proportion of object and image. For example, if the object is at infinity, the size of image is determined by the following formula y ′=-f ′· Tan ω （ ω Is the object field angle).
Relative aperture d/f'and aperture number f are the key optical indexes of lens in camera module. Relative aperture refers to the light energy that can enter the lens and reach the negative film, thus determining the illumination of the image plane. It is defined as the ratio of the pupil diameter D to the lens focal length F'. Photography of dark scenes and high-speed moving objects requires a large relative aperture objective lens, which can improve the illumination of the image plane. According to the size of the relative aperture, Photographic objective lens is divided into weak light objective lens (d/f'1:6.3 or below), ordinary objective lens (d/f'1:5.6-1:3.5), strong light objective lens (d/f'1:2.8-1:1.4) super light objective lens (d/f'1:1-1:0.8). In order to make the same lens use different environments, the aperture diaphragm usually adopts a continuously variable diaphragm.
Therefore, a good camera module not only gives you the choice of camera module, but also explains the choice of lens and chip of camera module in detail.
