11/10/2023
An article takes you through the camera
Yuntai Optics
Professional custom R&D and production of various car lenses, surveillance lenses, drone lenses, smart home lenses, etc.
Overview of the camera
Camera is a kind of video input device, also known as computer camera, computer eye, etc., which is widely used in video conferencing, telemedicine and real-time monitoring and other fields. With the development of Internet technology and the maturity of photosensitive imaging device technology, the price of cameras has gradually decreased, and it has become an affordable device for ordinary people. People can communicate and communicate with audio & video on the network through the camera, and can also be used for digital imaging, audio and video processing, etc.
Second, the classification of cameras
According to different digital signal processing methods, cameras can be divided into two categories: digital cameras and analog cameras.
2.1 Analog camera
The analog camera can convert the analog video signal generated by the video capture device into a digital signal and store it in the computer. The video signal captured by the analog camera must be converted into a digital mode by a specific video capture card and compressed before it can be converted into a computer for use. The overall cost of the analog camera is high, and it is no longer a mainstream product.
2.2 Digital Camera
Digital cameras can directly capture images and then transfer them to a computer through a serial, parallel or USB port. Digital cameras are now the main cameras on the market, and USB digital cameras using new data transmission interfaces are the main digital cameras. Most of the products currently on the market are such products. Due to the rapid popularity of personal computers, the transmission speed of USB interfaces is much higher than that of serial and parallel ports, so the current market hotspot is mainly digital cameras with USB interfaces. In addition, there is a product that works with video capture cards, but it is not yet mainstream.
III. How the camera works
When light passes through the camera lens (LENS), an optical image is formed inside the camera. This optical image is then projected onto the surface of the image sensor (SENSOR).
An image sensor is a semiconductor chip with hundreds of thousands to millions of photodiodes on its surface. When these photodiodes are illuminated by light, they generate electrical charges. These charges are called "pixels," and they record the details and color information of the image.
These charges are then converted to a digital signal through analog-to-digital conversion (A/D). Analog-to-digital conversion is the process of converting an analog signal into a digital signal, dividing the analog signal into discrete parts and representing those parts digitally. These digital signals are converted into digital image signals that can be processed by a computer.
The digital signal processing chip (DSP) is a key component in the camera. It receives the digital image signal from the image sensor and optimizes the digital image signal through a series of complex mathematical algorithms. For example, the DSP can adjust the brightness, contrast, color saturation, and sharpness of the image, improving image quality. These processed signals are then transmitted to a computer or other device via an interface such as USB. The structural framework of the DSP typically includes components such as an image signal processor (ISP), a JPEG image decoder (JPEG encoder), and a USB device controller.
Finally, the computer receives these processed digital image signals through the USB interface and displays them on the screen, allowing users to view and use them.
IV. Camera structure and components
4.1 Lens (LENS)
The lens of a camera is a lens structure composed of several lenses, which can be divided into plastic lenses and glass lenses. The main function of the lens is to focus, focusing the light of the scene on the camera's image sensor.
4.2 Image sensor (SENSOR)
Camera image sensors can be divided into two types: CCD (Charge Coupled Device) and CMOS (Complementary Metal Oxide Semiconductor). CCD sensors respond quickly to light and are suitable for high-speed shooting, while CMOS sensors are more power efficient and suitable for low-power applications.
4.3 Digital Signal Processing Chip (DSP)
Digital signal processing chip (DSP) is one of the core components of the camera. Major DSP manufacturers in the market include Songhan (SONIX) and VIMICRO. The main function of DSP is to process and compress image signals to transmit and store image data more efficiently.
4.4 Power Supply
The camera requires two operating voltages: 3.3V and 2.5V. Therefore, the power supply inside the camera is also a factor to ensure the stable operation of the camera.
Fifth, the main technical indicators of the camera
5.1 Resolution
Resolution refers to the size of the image that a camera can capture, usually expressed in pixels. Common resolutions include:
21 million pixels (5344 x 4016)
16 million pixels (4608 x 3408)
13 million pixels (4208 x 3120)
11 million pixels (4080 x 2720)
8 million pixels (3264 x 2488)
5 million pixels (2592 x 1944)
2 million pixels (1920 x 1080, also known as 1080P)
1 million pixels (800 x 600, also known as 720P)
VGA (640 x 480, also known as 300,000 pixels)
CIF (352 x 288, also known as 100,000 pixels)
5.2 Image Format/Color Space
The images captured by the camera can be in a variety of formats, including RGB24, I420, RGB565, RGB444, and YUV4:2:2. RGB24 and I420 are the two most commonly used formats. RGB24 represents R, G, and B colors with 8 bits each, and can express 256 shades, so that 256 x 256 x 256 colors can be reproduced. I420 is a YUV format, which is commonly used for video transmission and can compress and transmit video data more efficiently.
5.3 Automatic White Balance Adjustment (AWB)
Automatic white balance adjustment is a function in which the camera automatically adjusts the white balance of the image to ensure that the white object appears white on the screen in the image captured in different color temperature environments. Color temperature refers to the spectral composition and the color of light, while low color temperature indicates that there are more long-wavelength light components. When the color temperature changes, the camera needs to adjust the ratio of red, green and blue primary colors to achieve color balance.
5.4 Image compression methods
JPEG is a still image compression method. It is a lossy compression method. The higher the compression ratio, the worse the image quality. When image accuracy requirements are not high and storage space is limited, JPEG format can be selected. Most digital cameras use JPEG for image compression.
5.5 Color Depth
Color depth reflects the ability to recognize colors and the ability to represent colors in imaging. It is actually the quantization accuracy of the A/D converter, which refers to how many levels the signal is divided into. Usually expressed in color bits, common color depths are 8, 10, and 12 bits. The higher the color depth, the resulting image color
Six, in-depth understanding of the camera
Cameras are essential technical devices in modern life, but their quality is often overlooked. A good quality camera can present more realistic image effects, allowing users to take more satisfactory photos and videos. From the perspective of hardware composition, the quality of a camera is mainly determined by the following two aspects:
6.1 Lens (LENS)
The lens is the core component of the camera. It consists of several lenses, usually made of plastic lenses and glass lenses. The more complex the lens structure, the more lenses and the higher the cost. The common structures on the market currently include 1P, 2P, 1G1P, 1G2P, 2G2P, 4G, etc. Among them, cameras with glass lenses are of higher quality and have better imaging results than those with plastic lenses. However, in order to reduce costs, many camera products on the market use plastic lenses or semi-plastic and semi-glass lenses (i.e. 1P, 2P, 1G1P, 1G2P, etc.).
6.2 Image sensor (SENSOR)
Image sensors are divided into two categories: CCD (Charge Coupled Device) and CMOS (Complementary Metal Oxide Semiconductor). CCD sensors have high sensitivity, low noise, and large signal to noise ratio, but the production process is complex, high cost, and high power consumption; CMOS sensors have high integration, low power consumption (less than 1/3 of CCD), and low cost, but have relatively high noise, low sensitivity, and high light source requirements. Under the same pixel, CCD imaging quality is often better, including transparency, sharpness, color reproduction, and exposure accuracy.
In addition, more user-friendly, easier to use, and more practical application functions are also the development trend of cameras. For example, more and more cameras will have scanner functionality, as well as practical features such as facial recognition and voice interaction.
6.3 precautions for daily use of cameras
1. Protect the camera sensor device: Avoid facing the camera directly into the sun, and choose an appropriate location or install a sun visor to reduce the impact on the camera.
2. Avoid contact with harmful substances: Avoid camera contact with substances such as oil, steam, water v***r, moisture and dust. If it comes into contact, it should be cleaned immediately.
3. Clean the camera correctly: Use a special cleaner or water to wipe the surface of the camera, and avoid using highly irritating cleaners or organic solvents.
4. Connect the camera correctly: Avoid pulling or twisting the cable to ensure good contact between the camera and the cable.
5. Do not disassemble the camera at will: avoid opening the camera at will and trying to touch its internal parts, which can easily cause damage to the camera.
Analysis of camera technology
7.1 photosensitive elements: CCD and CMOS
On the market, mainstream cameras use CCD and CMOS, two types of photosensitive elements. The photosensitive elements can be analogous to the negatives of traditional cameras, and they convert optical signals into electrical signals. CCD photosensitive elements have high resolution and realistic color reproduction, so they have become the protagonist in megapixel digital photography equipment. CMOS photosensitive elements have the characteristics of energy saving and low cost, so almost all medium and low-end cameras use CMOS as photosensitive elements. However, CMOS cameras have higher requirements for light, and the resulting image is rougher than CCD.
7.2 Pixel value and resolution
Pixel value and resolution are two important indicators of a camera. Pixel value refers to the number of independent pixels in the image, which is determined by CCD or CMOS. Resolution is the ability of the camera to distinguish the image, and its maximum value is determined by the pixel value of the camera (except interpolation). On the current market, the pixel value of mainstream camera products is generally 300,000, 350,000 and 380,000, and there are 500,000 or even 1.30 million, but it is relatively rare and the price is very high. Resolution is the ability of the camera to distinguish the image, and its maximum value is determined by the pixel value of the camera (except interpolation). For example, 300,000 pixel cameras can provide a maximum resolution of 640 ร 480, but many chat software (such as MSN) supports a resolution of only 320 ร 240 by default, which is equivalent to 100,000 pixels. It should be noted that a large pixel value only means that the image will be more delicate and clear in theory, but the pixel value is not the only factor that determines the image quality. When purchasing, you should also ask whether the nominal pixel value is the real pixel or interpolation, because both are 7.3 frame rate.
In the image quality of the camera, in addition to pixel value and resolution, frame rate is also an important factor. Frame rate can be understood as the number of pictures sampled by the camera per second. The higher the frame rate, the higher the fluency of the picture. Generally speaking, only when the frame number of the picture refresh is more than 24 frames/second, the human eye will not detect obvious pauses.
Currently, due to cost constraints, mainstream cameras typically have a maximum frame rate of 30 frames per second, while lower-end products typically have only 15 frames per second or less. A better-performing camera should have the ability to achieve a maximum frame rate of 30 frames per second (352 x 288). It should have a refresh rate of 15 frames per second even when shooting in the standard VGA format (640 x 480).
7.4 The influence of lens and focal length
The lens is equivalent to the human eye in the camera, and whether the image is bright and clear often depends on the quality of the lens. Therefore, the cost of the lens accounts for a large proportion of the entire camera. Two cameras with the same pixel and function use different lenses, and the cost can vary greatly. Cheap plastic lenses will reduce costs, but will affect picture quality.
A good lens should be made of glass or fiberglass and consist of multiple lenses. At the same time, whether the lens is coated or not is also one of the factors that evaluate the quality of the lens. By looking at the lens from the side, you can see that the coated lens has a purple or blue-green luster. These lenses do not exist on lenses without coating.
When using a camera, if the picture is blurry, it is likely that the focal length is not properly adjusted. The camera uses a hyperfocal length, which means a large depth of field, but manual focus is required for macro. Hyperfocal length is the fastest way to get the maximum depth of field or control the clear range of the image. Point-and-shoot cameras generally use short-focal lenses to achieve hyperfocal length, so that the scene after a certain distance can be imaged more clearly, eliminating the need for focus function.
7.5 The Importance of Camera Processing Chips
Image processing chips are a very important factor affecting the imaging effect of cameras. These processing chips include DSPs, ISPs, image sensing modules, SOCs, etc., which are critical for decoding images and audio. If a product uses a poor quality chip, it will cause the camera to be unusable in poor light. Therefore, when choosing a camera, the quality of the processing chip is an important factor to consider.
7.6 CMOS camera and CCD camera
CMOS cameras and CCD cameras are two common types of cameras currently on the market. The main difference between them is the manufacturing process. CCD cameras are integrated on semiconductor single crystal materials, while CMOS cameras are integrated on semiconductor materials called metal oxides. However, in terms of working principle, they are not fundamentally different.
The main difference between CCD and CMOS in manufacturing is that CCD is integrated on a semiconductor single crystal material, while CMOS is integrated on a semiconductor material called metal oxide, and there is no essential difference in working principle. However, the CCD manufacturing process is more complicated, so the price of cameras using CCD is relatively high, and only a few manufacturers, such as Sony and Panasonic, have mastered this technology. The gap between the actual effect of CMOS and CCD has been reduced a lot. Since the manufacturing cost and power consumption of CMOS are much lower than that of CCD, products using CMOS photosensitive elements are more common in the camera field.
In terms of imaging, under the same pixel, the imaging transparency and sharpness of CCD are very good, and color reproduction and exposure can be basically guaranteed accurately. However, CMOS products are often generally transparent, and the color reproduction ability of the object is weak, and the exposure is not very good. Due to its own physical characteristics, CMOS imaging quality still lags behind that of CCD. However, by using advanced image control technologies such as automatic gain reinforcement technology for image light sources, automatic brightness, white balance control technology, color saturation, contrast, edge enhancement, and gamma correction, the effect comparable to that of CCD cameras can be achieved.
VIII. Camera market status and development
With the development of the digital product market, digital camera products on the market have become the main equipment for people to shoot life, record travel, and make videos. In digital cameras, CMOS photosensitive devices are mainstream. Cameras using CMOS photosensitive devices can perfectly restore images through advanced image control technologies such as automatic gain and reinforcement of image light sources, automatic brightness, white balance control technology, color saturation, contrast, edge enhancement, and gamma correction, achieving an effect comparable to CCD cameras.
However, although CCD image sensors have advantages in image quality, the number of camera manufacturers using CCD image sensors is small, mainly due to high cost. With the development of the market and the advancement of technology, it is believed that the application of CCD image sensors will be further popularized over time.
Looking to the future, with the continuous development of the digital product market, the application of cameras is becoming more and more extensive, and CMOS photosensitive devices have become the mainstream of digital cameras in the market. Through the continuous innovation and progress of image control technology, it can perfectly meet the needs of users for high-quality images. Although the cost of CCD image sensors is high, with the development of the market and the advancement of technology, it is believed that the application of CCD image sensors will gradually increase, providing users with more choices.
