Introduction to camera module

Mainly based on my own understanding of the camera, I will briefly introduce the structure of the camera module.

1.camera module structure

A camera module generally consists of the following parts, namely the lens, image sensor, base row and cable, as shown in the following figure:

If it is a camera module with AF function (usually a mobile phone camera), most of them use the VCM method, which has one more coil than the above structure, and the lens moves vertically by adding points to the coil to achieve the focusing function. If it is a camera with an anti-shake function, the lens can also move along the horizontal direction to achieve an optical anti-shake effect.

     The sensor we often say refers to the sensor soc packaged in the module, and the module is generally purchased by a special module factory after the sensor soc is selected according to the needs of different materials to produce modules of different specifications and quality, so although It is the same type of sensor, if it is produced by different module factories, then the connection and use of the circuit are also different, and the specific circuit needs to be based on the circuit diagram provided by the module factory. The ov2640 module we usually talk about refers to the module that uses the ov2640 soc inside. At the same time, even if it is a module produced by the same manufacturer, there will be multiple models due to different lenses or other hardware differences. The lens is also an important factor affecting the quality of the camera output image.

     For the datasheet of the camera picture, it refers to the datasheet that the original camera factory explained to the SoC; while the datasheet of the module refers to the optical characteristics and electrical interface description documents of a module factory that uses the sensor soc to make the module , we need to arrange the connection relationship between the schematic diagram and the main control according to the electrical connection sequence, or we need to ask the module factory to make a module suitable for the motherboard according to our main control circuit interface definition.

      Generally speaking, the module factory will also explain the model of vcm and the model of vcm driver.

Copyright statement: This article is an original article of CSDN blogger "fei…", following the CC 4.0 BY-SA copyright agreement, please attach the original source link and this statement for reprinting.

2.Camera module selection

The sensor and lens in the camera module generally account for more than 90% of the cost, and the resulting image quality is also determined by these two.

(1) Choose the most suitable sensor according to the price you can accept, the interface of the motherboard, and the resolution of the photo and video you need

     The price of the sensor usually accounts for 40%-60% of the module price. To ensure that the resolution/frame rate can meet the requirements and at a certain cost, choose a sensor with better light sensitivity and larger pixel area.

(2) According to the purpose of the sensor you need, choose a lens with a suitable size and field of view. If you need a lens with a large field of view, you can choose a fisheye camera (that is, a wide-angle camera that we usually call). However, for the pictures taken by the fisheye camera, there will be a distortion effect. In fact, if this distortion effect can also be corrected by itself.

     The chief ray angle (CRA) of the lens must be consistent with the CRA of the sensor. Generally speaking, a small amount of difference is allowed, otherwise the light will not be incident on the normal pixel photosensitive area after passing through the surface lens of the sensor. If the subsequent ISP does not handle it properly, A maze grid will appear on the screen. The reason why the sensor has CRA is that the microlens used for light collection on the surface has a FOV (Field of view) problem, so the excess light cannot be captured by the mobile phone; the CRA of LENS is the inclination angle between the pearl ray at the maximum image height and the optical axis; if If the LENS does not match the CRA of the sensor, the light cannot be effectively collected at a position with a high image height, and the shading will be aggravated;

Copyright statement: This article is an original article of CSDN blogger "fei…", following the CC 4.0 BY-SA copyright agreement, please attach the original source link and this statement for reprinting.