Camera module, full name of CameraCompact Module, abbreviated as CCM. CCM consists of lens, sensor, flexible board (FPC) and image processing chip (DSP). The important components that determine the quality of a camera are: lens, image processing chip (DSP) and sensor. The key technologies of CCM are: optical design technology, aspheric mirror manufacturing technology and optical coating technology.

Working principle: the light gathered by the lens of an object is converted into an electrical signal by CMOS or CCD integrated circuits, and then converted into a digital image signal by an internal image processor (ISP) and output to a digital signal processor (DSP) for processing, and converted into a standard image signal in GRB, YUV and other formats.

? Lens is a device that can receive optical signals and converge them on CMOS/CCD. The lens determines the daylighting rate of the sensor, and its overall effect is relative to a convex lens.

? The lens structure of a general camera is composed of several lenses, including plastic lens and glass lens. Generally, the lens structures used by a camera are: 1p, 2p, 1g 1p, 1g3p, 2g2p, 4g, 8p, etc. The more lenses, the higher the cost; Glass lens is more expensive than plastic lens, but the imaging effect of glass lens is better than plastic lens. At present, the mobile phone camera on the market is mainly 1G3P (composed of 1 glass lens and 3 plastic lenses), in order to reduce the cost.

A, eliminate flash as much as possible

B, picture quality clarity

C, CRA (main light angle) to match, reduce the shadow (lens CRA

D, the larger the aperture, the better.

E, the distance should be as small as possible.

(1) focal length: The focal length of the lens determines the imaging size, viewing angle, depth of field and perspective of the picture. Generally speaking, for a single lens, it is the distance from the center of the lens to the focus, while the camera lens is composed of multiple lenses, which is much more complicated. The focal length here refers to the distance from the center point of the lens to the clear image formed on the CCD.

(2) Angle of view: We often use the horizontal angle of view to reflect the shooting range of the picture. The larger the focal length f, the smaller the field of view angle, and the smaller the picture range formed on the photosensitive element; Conversely, the smaller the focal length f, the larger the field of view angle and the larger the picture range formed on the photosensitive element.

(3)F value (aperture ratio): F value refers to the brightness of the lens (that is, the light transmittance of the lens). F= lens focal length/aperture diameter. Under the same F value, the aperture of a long focal length lens is larger than that of a short focal length lens.

(4) Aperture: Aperture is an adjustable optical mechanical aperture located in the lens, which can be used to control the amount of light passing through the lens. Iris diaphragm A mechanical device inside a lens used to control the aperture size. Or a device for opening or closing the lens aperture to adjust the f-stop of the lens.

(5) Depth of field: When the object is clearly focused, all the scenes within a certain distance from the front to the back of the object are also quite clear. The distance from front to back with a fairly clear focus is called depth of field.

? Voice coil motor, a voice coil motor in electronic products, is a kind of motor. Because the principle is similar to the sound box, it is called voice coil motor, which has the characteristics of high frequency response and high precision. Its main principle is to control the stretching position of the spring by changing the DC current of the magnetic coil in the permanent magnetic field, so as to drive the spring to move up and down. VCM is widely used in mobile phone cameras to realize auto-focusing function. Through VCM, the position of the lens can be adjusted to present a clear image.

? The performance of VCM mainly depends on the ratio of current to stroke. Starting from the starting current, the current rise should be proportional to the distance that can be driven. The smaller the required rising current, the higher the accuracy. At the same time, it also depends on the maximum power consumption, maximum power and size.

Structurally, it can be roughly divided into three categories: (1) elastic sheet structure; (2) Spherical structure; (3) Friction structure.

Functionally, it can be roughly divided into five categories: (1) open-loop motors; (2) closed loop motor closed loop; (3) standby intermediate motor; (4)OIS optical anti-shake motor (translation type, shaft moving type, memory metal type, etc.). ); (5)OIS+ closed-loop six-axis motor.

? After entering the autofocus mode, the driver moves from 0 to the maximum, so that the lens moves from the original position to the maximum displacement. At this time, the imaging plane of the sensor automatically takes pictures and saves them in DSP. DSP calculates the MTF (modulation transfer function) value of each picture through these pictures, so as to find the maximum value in this MTF curve. Through the algorithm, the current corresponding to this point is obtained, and the driver is instructed to provide this current to the voice coil again, thus stabilizing the lens on this imaging plane and realizing automatic zooming.

A: ZOOM motor is used to realize optical zoom.

By moving the lens inside the lens, changing the position of the focus, changing the length of the focal length of the lens and changing the viewing angle of the lens, the influence can be enlarged and reduced.

B: The focusing motor is used to realize automatic focusing.

Move the position of the whole lens (not the lens in the lens) a tiny distance, control the focal length of the lens, and realize the clarity of the image. Common methods in mobile phones.

Optical focusing and optical zooming are different concepts:

Optical zoom is to change the position of focus, the length of focal length and the viewing angle of the lens by moving the relative position of the lens inside the lens, so as to enlarge and reduce the image.

Optical focusing actually controls the image distance by adjusting the position of the whole lens (rather than the position of the lens in the lens), so as to make the imaging clearest.

? There are various wavelengths of light in nature. The wavelength range of light that human eyes can recognize is between 320 nm and 760 nm, and the light beyond 320 nm to 760 nm is invisible to human eyes. The imaging component of the camera, CCD or CMOS, can see most wavelengths of light. Due to the participation of all kinds of light, the color restored by the camera is different from that seen by the naked eye. For example, green plants turn gray, red pictures turn light red and black turns purple. At night, due to the filtering effect of bimodal filter, CCD can't make full use of all the light, and it doesn't produce snowflake noise, so its low illumination performance is not satisfactory. In order to solve this problem, infrared cut-off double filters are adopted.

? The IR-CUT double filter means that the camera lens group has a set of filters built in. When the infrared sensor outside the lens detects the change of light intensity, the built-in IR-CUT automatic switching filter can automatically switch according to the intensity of external light, thus achieving the best image effect. In other words, the dual filters can automatically switch filters during the day or night, so the best imaging effect can be obtained during the day or night.

? The infrared cut-off double-filter switch consists of an infrared cut-off low-pass filter (infrared cut-off or absorption filter), full-spectrum optical glass (full-spectrum filter), a power mechanism (which can be electromagnetic, motor or other power sources) and a shell, and is switched and positioned through a circuit control board. When there is enough light in the daytime, the circuit control board drives the switch to switch and position the infrared cut-off filter to work, and the CCD or CMOS restores its true color; When the visible light is insufficient at night, the infrared cut-off filter is automatically removed, and the full-spectrum optical glass starts to work. At this time, the infrared light of the infrared lamp can be sensed, so that CCD or CMOS can make full use of all the light, thus greatly improving the night vision performance of the infrared camera and making the whole picture clear and natural.

A. Infrared cutoff, transmittance and light shaping effect of the filter.

B, power drive part

C, control circuit

4. Filter: Generally, infrared light is filtered by IR coating or blue glass.

? An image sensor is a semiconductor chip with millions to tens of millions of photodiodes on its surface. When photodiodes are illuminated, they generate charges and convert light into electrical signals. Its function is similar to human eyes, so the performance of the sensor will directly affect the performance of the camera.

Photosensitive components: CCD, CMOS(PPS and APS)

Different processes: front-illuminated FSI, back-illuminated BSI, stacking.

1. pixels

? There are many photosensitive units on the sensor, which can convert light into charge, thus forming an electronic image corresponding to the scene. In the sensor, each photosensitive unit corresponds to a pixel. The more pixels, the more details it can perceive, so the clearer the image. The higher the pixel, the clearer the imaging effect. The product of camera resolution is the pixel value, for example: 1280×960= 1228800.

2. Target size

? The size of the photosensitive part of an image sensor is usually expressed in inches. Like TV sets, this data usually refers to the diagonal length of the image sensor, such as 1/3 inches. The larger the target surface, the better the luminous flux, while the smaller the target surface, the easier it is to obtain a greater depth of field.

3. Sensitivity

? That is, the intensity of incident light is sensed by CCD or CMOS and related electronic circuits. The higher the sensitivity, the stronger the sensitivity of the photosensitive surface to light, and the higher the shutter speed, which is particularly important when shooting moving vehicles and monitoring at night.

4. Electronic switch

? It is a term put forward by comparing the mechanical shutter function of the camera. It controls the exposure time of the image sensor. Because the photosensitive value of the image sensor is the accumulation of signal charge, the longer the photosensitive time, the longer the accumulation time of signal charge and the greater the amplitude of output signal current. The faster the electronic shutter, the lower the sensitivity, which is suitable for shooting under strong light.

5. Frame rate

? Refers to the number of pictures recorded or played per unit time. Playing a series of pictures in succession will produce an animation effect. According to the human visual system, when the playing speed of a picture is greater than 15 frames per second (that is, 15 frames), the human eye can hardly see the jump of the picture. When it reaches 24 -30 frames per second (i.e. 24-30 frames), the flicker phenomenon is basically imperceptible.

? Frames per second (fps) or frame rate indicates the number of times that the graphics sensor can be updated per second when processing the field. High frame rate can get a smoother and more realistic visual experience.

6. Signal to noise ratio

? Is the ratio of signal voltage to noise voltage, and the unit of signal-to-noise ratio is expressed in dB. Generally, the signal-to-noise ratio (SNR) values given by cameras are the values when AGC (Automatic Gain Control) is turned off, because when AGC is turned on, small signals will be enhanced and the noise level will be increased accordingly.

? The typical signal-to-noise ratio is 45-55 dB. If it is 50dB, the image is a little noisy, but the quality is good. If it is 60dB, the picture quality is excellent and there is no noise. The greater the signal-to-noise ratio, the better the noise control. This parameter is related to the number of noise points in the image. The higher the signal-to-noise ratio, the clearer the image and the less the point noise in the night vision image.

? DSP (DIGITAL SIGNAL PROCESSING) function: It mainly optimizes the parameters of digital image signals through a series of complex mathematical algorithms, and transmits the processed signals to PC and other devices through USB and other interfaces.

Noun explanation:

ISP is the abbreviation of Image Signal Processor, that is, image signal processor.

DSP is the abbreviation of digital signal processor.

Functional explanation:

ISP is generally used to process the output data of image sensors, such as AEC (automatic exposure control), AGC (automatic gain control), AWB (automatic white balance), color correction, lens shading, gamma correction, removing bad spots, automatic black level, automatic white level and so on.

DSP has many functions. It can do some photo and echo (JPEG codec), video and playback (video codec), H.264 codec and many other processing. In short, it can process digital signals.

Reference link: