Camera module and related concepts

1. Basic structure of Camera module

The core structure is Lens, IR Filter and Sensor three parts.

Lens consists of several lenses. Glass lenses are good for imaging but expensive. The advantage of multiple lenses is that they can filter, converge, and correct light layers.

IR Filter is infrared filter;

The Sensor is the core component that functions like the film of a film camera and is responsible for imaging. There are two types: CCD and CMOS, CCD sensitivity and resolution is better, generally used in digital cameras, CMOS cost, yield, power consumption is better, generally used in mobile phones.

Lens Main technical parameters

Resolution: The resolution of the camera is related to the resolution of the lens and sensor.

Field of View (FoV) : Field of view Angle.

Focus Length: The distance between the focal point of the lens and the center of the lens. The focus of the image is the clearest. DOF: The area that remains clear within a certain range before and after the focus. It is related to aperture, object distance, focal length and sensor. The larger the aperture or the closer the object, the smaller the depth of field.

Aperture coefficient F: F (aperture coefficient value) = f (focal length)/D (aperture hole diameter). In actual use, the aperture coefficient is usually used to indirectly express the size of the relative aperture, such as f/1.4, f/2, f/2.8, and f/1.4 is equivalent to F1.4. The reciprocal of the aperture coefficient is called the relative aperture. Aperture controls the amount of light, depth of field and image quality.

TV distortion: barrel or pillow deformation.

Main technical specifications of Sensor

ISO: Sensitivity of the sensor to light.

Dark shading/current(mv/sec, pA/cm2) : sensor image noise. At room temperature, in a completely dark environment, the voltage generated by the pixel in 1 second.

Dynamic Range(dB) : Ratio of maximum unsaturated photocurrent to minimum detectable photocurrent. DR = 20log10 (i_max/i_min).

Signal-to-noise ratio(dB) : The ratio of Signal voltage to Noise voltage.

White balance: restores white objects to white under any light source. The measurement accuracy index is the color difference ∆C between the actual color and the ideal color after the white balance is stabilized, which should generally be within 10.

2. Camera related concepts

AF (Auto Focus) Indicates the automatic focus.

OIS (Optical Image Stabilizer) Optical image stabilization device: anti-stabilization. Adjust the Compensation lens through negative feedback. Compared with the traditional camera more gyroscope, voice coil motor and driver IC.

voice coil motor (VCM) : Used for auto-focus and anti-shake, it can adjust the position of the lens.