Knowledge about CCD, CMOS, and lenses
We are often asked by customers about CCD, CMOS, and lens related knowledge. Now we have compiled some parameters and knowledge related to CAMERA, hoping to be useful to customers. Originating from the website.
Currently, cameras are used on many multimedia devices, including mobile devices, and are constantly being updated at a fast pace. There are currently two types of cameras in use: CCD (Charge Coupled Device) and CMOS (Complementary Metal Oxide Semiconductor).
These two types have their own advantages and disadvantages: currently, CCD mainly uses high-quality DC, DV, digital cameras, and high-end mobile phones, which have good image quality. However, the entire driver module is relatively complex, and currently only some Japanese companies have mastered its production technology. For the selected manufacturers, the cost will be relatively high, and some devices do not have very strict requirements for image quality, with higher volume requirements; And CMOS precisely meets such requirements, while CMOS modules are relatively simple. Currently, many manufacturers have integrated ISP (Image Signal Processor) drivers and signal processing inside the module, making it smaller in size. Moreover, its production technology requirements are relatively simple, the process is mature, the cost is low, the peripheral circuit is simple, and the image quality can also meet general requirements. Therefore, it occupies a large share in the embedded market. Currently, the quality of some high-end CMOS sensors can be comparable to that of CCD.
Sensors can generally be classified into CCD and CMOS based on their photosensitive components
| Comparison point | CCD camera | CMOS camera |
| Advantage | ● High sensitivity ● Low noise ● The image quality is good ● The shutter speed is fast ● High consistency of pixel response |
● Digital and analog circuits can be added to the chip ● High cost-effectiveness; low price ● Special chips can be equipped with simple processing functions ● Single-channel output; high dynamic range ● It can output continuously or randomly without relying on storage media; it has high speed |
| Disadvantage | ● High cost ● Low speed ● Window limitation ● The system has high complexity ● High power consumption |
● low sensitivity ● High noise level, low image quality ● Non-uniform pixel response ● Partially adopting rolling shutter ● The shutter is not controllable |
2.1 Basic structure
Lens: lens structure, made of plexiglass and quartz;
Lens Base: Used for securing the lens
Image sensor:
CCD (charge-coupled device): charge-coupled device
CMOS (complementary metal oxide semiconductor): complementary metal-oxide-semiconductor
DSP digital processing circuit: AD converter
Power Supply: Two operating voltages: 3.3V and 2.5V;
The aperture can adjust the amount of light entering the lens. For example, a domesticated cat’s pupil always contracts into a line during the day and automatically opens into a round hole at night. Similarly, when taking photos, if the light is strong, the aperture should be narrowed, and if the light is dim, the aperture should be widened. That is to say, a camera with a smaller F-number (other parameters being the same) is more conducive to night photography.
The maximum diameter circle imaged by the circular optical system depends on or is determined by the size of the sensor used in conjunction.
9）TV distortion
2.1.2 IR Filter (Infrared Filter)
Function: Remove infrared light, avoid infrared interference, correct incoming light, improve sensor proximity interference, and make the colors presented in the image match the perception of the human eye.
Classification: Generally, it is divided into interferometric IR/AR-CUT (coating on a low-pass filter wafer, utilizing the principle of interference cancellation) and absorptive glass (utilizing the principle of spectral absorption).
Influencing factors: For IR-CUT, it is not related to the thickness of IR-CUT, but mainly depends on the coating process control and the number of coating layers. For glass, it is related to the thickness, with thicker glass being better. Additionally, for high-end products, there is also a type of blue glass called IRCF
For the mobile phone camera: 1) For the visible light spectrum range: 430-620nm, there is a transmittance requirement, Tmin>=85%. 2) For the filtered wavelength range: 650+/-10nm, there is a filtering requirement, T<=50%. 3) For the near-infrared spectrum range: 700-1200nm, there is a transmittance requirement. 4) For the AR (Anti-Reflective) surface, there is a reflectance requirement for visible light in the range of 420-670nm
The working principle of the sensor
Actually, the light-sensing part of a sensor is composed of multiple pixels arranged according to a certain pattern.
Light —> Charge —> Weak Current —> RGB Digital Signal Waveform —> YUV Digital Signal
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