The composition and working principle of mobile phone cameras

The composition and working principle of mobile phone cameras

The mobile phone camera is composed of: PCB board, lens, holder and color filter, DSP (for CCD), sensor and other components.

The working principle is: the scene is shot through the lens, and the generated optical image is projected onto the sensor. Then the optical image is converted into an electrical signal. The electrical signal is then converted into a digital signal through analog-to-digital conversion. The digital signal is processed by DSP and then sent It is processed in the mobile phone processor and finally converted into images that can be seen on the mobile phone screen.

PCB board
Printed circuit boards used in cameras are divided into three types: hard boards, soft boards, and soft-hard combined boards.

lens
The lens is a device that images the scene on the sensor. It usually consists of several lenses. From the material point of view, camera lenses can be divided into plastic lenses and glass lenses.

The lens has two more important parameters: aperture and focal length.

The aperture is a device installed on the lens to control the amount of light that passes through the lens and reaches the sensor. In addition to controlling the amount of light, the aperture also has the function of controlling the depth of field. The larger the aperture, the smaller the depth of field. When taking portraits, the hazy background effect is caused by a small depth of field. A manifestation.

Depth of field refers to the distance range in front of and behind the subject measured by imaging that can obtain a clear image in front of the camera lens.

The smaller the value, the larger the aperture, the more light that enters, the brighter the picture, the narrower the focal plane, and the greater the subject background blur;

The larger the value, the smaller the aperture, the less light that enters, and the darker the picture. The wider the focal plane, the clearer the front and rear of the subject.

Focal length is the distance from the center point of the lens to the plane of the sensor where a sharp image forms.

According to the imaging principle, the focal length of the lens determines the size of the image formed on the sensor by the object captured by the lens. For example, when photographing the same object, the longer the focal length, the larger the image of the object can be captured. Long focal length is similar to a telescope.

Analysis of basic knowledge of mobile phone camera
Pixel: What is usually called "XXX million pixels" actually refers to the resolution of the camera. Its numerical value is mainly determined by the number of pixels (i.e., the smallest photosensitive unit) in the camera sensor. For example, 5 million pixels means that there are 500 pixels in the sensor. Ten thousand pixels are the same as the number of pixels in a mobile phone screen that determines whether the screen has a resolution of 720p or 1080p.

Pixels determine photo quality?

It is generally thought that the higher the pixels of the camera, the clearer the photos taken, in fact. The only thing that the camera's pixels can determine is the resolution of the pictures it takes. The higher the resolution of the picture, it only means that the size of the picture is larger, but it does not mean that the picture is clearer.

However, the current mainstream mobile phone screens are 1080p level (1920×1080 pixels). Whether it is a 4208×3120 pixel photo taken by a 13-megapixel camera or a 3200×2400 pixel photo taken by an 8-megapixel camera, it is beyond the interpretation range of a 1080p screen. , will eventually be displayed with 1920×1080 pixels, so there is no difference in the clarity seen by the naked eye.

So what are the advantages of high pixels?

The size of the picture taken by a camera with higher pixels is larger. If we want to print the sample, based on the conventional printing standard of 300 pixels/inch, the 4208×3120 pixel sample taken by the 13-megapixel camera can print 17 inch photos, while the 3200×2400 pixel sample from an 8-megapixel camera starts to blur when printed over 13 inches. Obviously, the 13-megapixel camera sample can be printed in a larger size.

Since pixels are not the key factor in determining picture quality, who is? The answer is sensors.

There are two main types of camera sensors: CCD and CMOS. Although CCD sensors have good image quality, they are expensive and are not suitable for mobile phones. CMOS sensors are the most widely used in the field of mobile phones due to their lower power consumption, price and excellent image quality.