Do You Know What Is Camera ?

1. What is Camera ?

Camera , we also call pc camera, computer eye, etc. As a video input device, it has been widely used in video conferencing, telemedicine and real-time monitoring in the past.

In recent years, dure to with the development of Internet technology, the continuous improvement of network speed, coupled with the maturity of photosensitive imaging device technology and large-scale use in the manufacture of cameras, this has reduced its price to a level that ordinary people can afford.

More and more people can also talk and communicate with each other on the network through the camera with audio and video. Besides, people can also use it for various popular digital images, audio, and video processing.

2.  The Classification Of The Camera

Cameras have two categories: digital cameras and analog cameras.

The analog camera can convert the analog video signal generated by the video acquisition device into a digital signal, and then store it in the computer. The video signal captured by the analog camera must be converted into a digital model by a specific video capture card and compressed before it can be converted to a computer for use.

While the digital camera can directly capture the image, and then pass it to the network through the serial, parallel, or USB interface. At present, the cameras on the computer market are basically digital cameras, and the digital cameras are mainly USB digital cameras using a new data transmission interface.

Most of the products currently visible on the market are these products. In addition, there is a product that works with video capture cards, but it is not now mainstream.

Due to the rapid popularity of personal computers and the high overall cost of analog cameras,what’s more the transmission speed of the USB interface is much more top than that of serial and parallel ports. That’s why the hot spot in the market is mainly digital cameras with USB interface.

3. The Working Principle Of The Camera

The working principle of the camera is roughly: the optical image generated by the scene is projected onto the surface of the image sensor through LENS, and then converted into an electrical signal, which is converted into a digital image signal after A / D conversion, and then sent to the DSP for processing and then through the USB interface Transfer to the computer for processing, and you can see the image through the monitor.

Note 1: SENSOR is a semiconductor chip, and its surface contains hundreds of thousands to millions of photodiodes. When the photodiode is exposed to light, it generates electrical charge.

Note 2: DSP (DIGITAL SIGNAL PROCESSING) function: It is mainly through a series of complex mathematical algorithm operations to optimize the processing of digital image signal parameters, and pass the processed signal to PC and other equipment through the USB interface. DSP structure framework:

1) ISP (image signal processor)

2) JPEG encoder

3) USB device controller

4. The Main Structure And Components Of The Camera

The working principle of the camera can list by the main structure and components of the camera

1) LENS

The lens structure is composed of several lenses, with plastic lens or glass lens.

Generally, the lens structures used for cameras are: 1P, 2P, 1G1P, 1G2P, 2G2P, 4G, etc. The more lenses, the higher the cost; glass lenses are more expensive than plastic. Therefore, a good quality camera should use a glass lens. And the imaging effect will be better than that of a plastic lens. In order to reduce costs, most camera products on the market generally use plastic lenses or semi-plastic semi-glass lenses (ie: 1P, 2P, 1G1P, 1G2P, etc.)

2) SENSOR have two categories:

CCD (charge couple device): charge coupled device

CMOS (complementary metal oxide semiconductor): complementary metal oxide semiconductor

CCD has the advantages of high sensitivity, low noise and high signal-to-noise ratio. But the production process is complex, the cost is high, and the power consumption is high. CMOS has the advantages of high integration, low power consumption (less than the 1AGU3 of CCD) and low cost. However, it hasa disadvantages high noise, low sensitivity and high demand for light source.

3) DSP

There are many DSP manufacturers, and the most popular ones on the market are: SONIX, VIMICRO, etc.

4) Power supply

There have two working voltages inside the camera: 3.3V and 2.5V. So a good camera internal power supply is also a factor to ensure the stable operation of the camera.

5. Some technical indicators of the camera

1) Image resolution / resolution (Resolution):

● SXGA (1280 x1024)

● XGA (1024 x768)

● SVGA (800 x600)

● VGA (640×480) means 0.3MP, (0.35MP refers to 648X488)

● CIF (352×28)

● SIF / QVGA (320×240)

● QCIF (176×144)

● QSIF / QQVGA (160×120)

2) Image Format / Color space: RGB24, I420 are currently the two most commonly used image formats.

● RGB24: Represents 8 colors of each of R, G, and B colors, and can express up to 256 shades, so that 256 * 256 * 256 colors can be reproduced.

● I420: one of YUV format.

● Other formats: RGB565, RGB444, YUV4: 2: 2, etc.

3) Automatic white balance adjustment (AWB)

Definition:It is required that the image on the screen should be white under different color temperature environments. The color temperature indicates the spectral component, means the color of light. Low color temperature means that there are many long-wave components. When the color temperature changes, the ratio of the three primary colors (red, green, and blue) in the light source will change. To achieve color balance that can adjust the ratio of the three primary colors. This is the actual adjustment of white balance.

4) Image compression method

JPEG: (joint photographic expert group)

Still image compression method. This is a compression method for lossy images. The greater the compression ratio, the worse the image quality. This format can be selected when the image accuracy is not high and the storage space is limited. However, most digital cameras currently use the JPEG format.

5) Color depth (Color Bit)

Reflects the ability to recognize colors and the color expression capabilities of imaging

The actual quantization accuracy of the A / D converter refers to how many levels the signal is divided into. Commonly used color bits said. The higher the color depth, the more vivid and attractive the color of the obtained image.

6) Image noise refers to noise in the image. Appears as a fixed color noise in the image.

7) FOV

Imaging with the human eye is a principle of integration, which is simply the imaging range.

8) Output / input interface

● Serial interface (RS232/422): slow transmission rate, 115kbit/s

● Parallel interface (PP): the rate can reach 1Mbit/s

● Infrared interface (IR DA): the rate is also 115kbit/s, which is commonly apply in notebook computers

● Universal Serial Bus USB: plug and play standard, supports hot plug and unplug. The speed of USB1.1 can reach 12 Mbit, and the speed of USB 2.0 can reach 480 Mbit/s.

● IEEE1394 (FireWire) interface (also known as ilink): its transmission rate can reach 100M ~ 400Mbit / s

At present, the digital cameras sold in the market are mainly CMOS photosensitive devices.

In the products using CMOS as photosensitive components, the effect is comparable to that of CCD camera by using advanced image control technology, such as automatic gain enhancement technology of image light source, automatic brightness and white balance control technology, color saturation, contrast, edge enhancement and gamma correction.

But the limited by the market situation and market development, there are few manufacturers using CCD image sensor for camera, mainly caused the high cost of using CCD image sensor.

Britech is a professional manufacturer specializing in designing, developing, manufacturing and marketing of all kinds of camera modules.

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