The principle of digital camera?

In today's digital wave, new technologies and products are increasingly affecting our lives. It has become a new fashion to own digital products. The camera is undoubtedly the closest to our daily life, and the digital camera may replace the traditional camera with its unique performance and characteristics. What is a digital camera? What are its characteristics? How to choose and use? Let's introduce it to everyone.

1. What is a digital camera?

The so-called digital camera is a special camera that can shoot and convert the shot scene into an image stored in digital format through internal processing. Different from ordinary cameras, digital cameras do not use film, but use fixed or detachable semiconductor memory to save the collected images. A digital camera can be directly connected to a computer, TV or printer. Under some conditions, digital cameras can also be directly connected to mobile phones or handheld computers. Because the image is processed internally, users can immediately check whether the image is correct, and can immediately print it out or send it by email.

2. The characteristics of digital camera:

Compared with traditional cameras, digital cameras still have a certain gap in shooting quality. However, it also has incomparable advantages over traditional cameras:

Compared with traditional cameras, digital cameras have the following five major differences: different manufacturing processes, different shooting effects, different shooting speeds, different storage media and different input and output modes. The biggest difference lies in the way images are recorded. Please take a look at the following process first:

Traditional camera: lens-> Photographic base plate

Digital camera: lens-> Photosensitive chip->; Digital processing circuit->; Storage plug-in

Digital cameras are basically the same as traditional cameras in image acquisition, mainly including shooting lens, viewfinder lens, flash, photoreceptor and self-timer indicator, so only looking at the front appearance of the camera, there is not much difference between them, but there is a big difference in imaging and recording. Traditional cameras use negatives, while digital cameras mainly rely on photosensitive chips and memory cards.

Although the price of digital camera is more expensive than that of traditional camera, it has many advantages that traditional camera does not have:

1. You can see immediately:

If you shoot with a traditional camera when traveling or attending some important dates, and then develop it after you come back, you suddenly find that the shooting quality is not right, such as too bright, too dark, the theme is blocked or even there is no image at all, then the mood is really indescribable. However, this will not happen to digital cameras, because almost all digital cameras will have something called a liquid crystal display (LCD), which can immediately display the image just taken. If there is something wrong, you can delete the image and shoot it again until you are satisfied.

2. Regardless of the shooting cost:

When shooting with a traditional camera, you will usually be very careful, and you will not shoot again in the same background, so as not to increase the printing cost. But don't worry about using a digital camera, because you can choose slowly after shooting, take the best image and print it, and the rest can be deleted or stored in the hard disk.

3. The image quality will never change:

Recording images with negatives or photos will fade and deteriorate over time, and the original quality cannot be maintained. On the contrary, the images taken by digital cameras only record the data of "0" and "1", which can be correctly stored in computer hard disks and other storage media, so digital images can maintain the same quality no matter how many times they are copied.

4. It can be directly edited and used:

Images taken with a digital camera can be directly downloaded to a computer, and then the images can be immediately transmitted to other people or customers by e-mail without spending money and time on printing. In addition, digital images can also be applied to web design, and the company's products can be promoted to every place in the world through its own website, which is really an indispensable weapon for e-commerce.

5. Less storage space:

The image taken by a digital camera is just a pile of data. Just use some small storage devices, such as hard disk, flash card, MO, etc. It can store many images, which is much more economical than using traditional cameras to put negatives and photos.

3. The principle and structure of digital camera:

A digital camera is composed of lens, CCD, A/D (analog-to-digital converter), MPU (microprocessor), built-in memory, LCD (liquid crystal display), PC card (removable storage) and interfaces (computer interface, TV interface). Usually, they are installed in digital cameras, but of course, the LCD of some digital cameras is separated from the camera body.

The working principle of a digital camera is as follows: when the shutter is pressed, the lens focuses the light on the photosensitive device CCD (Charge Coupled Device), which is a semiconductor device, replacing the position of the film in the ordinary camera, and its function is to convert the optical signal into an electrical signal. In this way, we get the electronic image corresponding to the shooting scene, but it can't be sent to the computer for processing immediately. We need to convert the analog signal into digital signal according to the requirements of the computer. ADC (Analog-to-Digital Converter) equipment is used to perform this work. Next, MPU (Microprocessor) compresses the digital signal and converts it into a specific image format, such as JPEG format. Finally, the image file is stored in the built-in memory. At this point, the main work of the digital camera has been completed, and the next thing to do is to view the photos taken through LCD (liquid crystal display). Some digital cameras use mobile storage to expand storage capacity, such as PC cards or floppy disks. In addition, it also provides an interface to connect the computer and the TV. Now, let's talk in detail:

1. lens:

Almost all digital camera lenses have a short focal length. If you look at the logo on the lens of a digital camera, you may find something like "f=6mm", and its focal length is only 6mm! In fact, this focal length is different from that of traditional cameras. F=6mm is equivalent to the 50mm lens of an ordinary camera (the camera is different from the camera). What's going on here? It turns out that the standard lens, wide-angle lens, telephoto lens and fisheye lens in our impression are all aimed at 35mm ordinary cameras. They are used for general photography, landscape photography, figure photography and special photography respectively. Different lenses have different focal lengths and shooting angles, and different shooting effects are also different. However, one condition that the focal length determines the viewing angle is the imaging size. The imaging size of a 35mm ordinary camera is 24mm×36mm (film), while the imaging size of a CCD in a digital camera is less than twice or even ten times this value. If the imaging size is smaller, the same viewing angle can be obtained. So the 6mm lens mentioned above is equivalent to the 50mm focal length lens of an ordinary camera. Therefore, when purchasing a digital camera, we don't have to care about the actual focal length of the digital camera, just refer to the focal length converted into a 35 mm camera lens.

2.CCD:

Digital cameras use CCD to replace the film of traditional cameras, so CCD technology has become the key technology of digital cameras, and the resolution of CCD is regarded as an important basis for evaluating the grade of digital cameras. CCD is the abbreviation of charge-coupled device, which is called photo-charge-coupled device. It is a surface photoelectric device made of microelectronic technology, which can realize photoelectric conversion function. It is widely used in cameras, digital cameras and scanners. Camera uses dot-matrix CCD, scanner uses linear CCD, and digital camera uses both dot-matrix CCD and linear CCD. Generally, digital camera uses dot-matrix CCD, and scanning digital camera specially shoots static objects uses linear CCD, which sacrifices time for the extremely high resolution (up to 8400×6000) comparable to traditional film. There are many photosensitive units on the CCD device, which can convert light into charge, thus forming an electronic image corresponding to the scene. Each photosensitive unit corresponds to a pixel in the image. The more pixels, the clearer the image. If we want to improve the clarity of the image, we must increase the number of photosensitive units of CCD. The specifications of digital cameras often give multiple resolutions at the same time, such as 640×480, 1024×768. The product of the highest resolution is 786,432 (1024× 768), which is the approximate number of 850,000 pixels of CCD photosensitive unit. So when we see the words "850,000 pixel CCD", we can estimate the maximum resolution of the digital camera.

Many early digital cameras adopted the above resolution, which can provide enough pixels for the pictures displayed by computers, because the resolutions of most computer graphics cards are 640×480, 800×600, 1024×768, 1 152×864, etc. CCD itself can't distinguish colors, it's just a photoelectric converter. There are many ways to realize color photography, including applying CFA (color filter array) on the surface of CCD device, or using light splitting system to divide light into three colors, red, green and blue, which are received by three CCDs respectively.

3. Analog-to-digital converter:

A/D converter is also called ADC (analog-digital converter), that is, analog-to-digital converter. It is a device that converts analog electrical signals into digital electrical signals. The main indexes of A/D converter are conversion speed and quantization accuracy. Conversion speed refers to the time required to convert analog signals into digital signals. Due to the huge number of pixels in high-resolution images, the conversion speed is very high, and the price of high-speed chips is correspondingly high. Quantization accuracy refers to how many levels an analog signal can be divided into. If the CCD quantizes the actual scene into several pixels in X and Y directions, the A/D converter quantizes the brightness or color value of each pixel into several levels. This level is called color depth in digital cameras. The technical indicators of digital cameras give the color depth value without exception, so how much does the color depth affect the shooting effect? In fact, the color depth is the number of digits of a color, with binary digits as the unit, and the number of colors is expressed by digits. Common ones are 24, 30 and 36 bits. Specifically, each primary color is represented by 8 bits or 10 bits in middle and low-grade digital cameras and 12 bits in high-grade cameras. The total color depth of the three primary colors of red, green and blue is the number of primary colors multiplied by 3, that is, 8×3=24 bits, 10×3=30 bits or 12×3=36 bits. The color depth of a digital camera reflects the number of colors that a digital camera can correctly represent. Taking 24 bits as an example, the three primary colors (red, green and blue) each occupy 8 bits of binary numbers, that is to say, red can be divided into 2 8 = 256 different grades, and so can green and blue, so their combination is 256× 256× 256 = 1677 72655. The higher the color depth value, the more realistic the color is.

4.MPU (microprocessor):

A digital camera must have a complete control system to realize metering, operation, exposure, flash control, shooting logic control and image compression. Digital camera realizes the unified coordination and control of all operations through MPU (microprocessor unit). Like traditional cameras, exposure control of digital cameras can be divided into manual and automatic. Manual exposure means that the photographer adjusts the aperture size and shutter speed. Automatic exposure can be divided into programmed automatic exposure, aperture priority exposure and shutter priority exposure. MPU adjusts the aperture and shutter by analyzing the sensitivity of CCD, and then adjusts the exposure by mechanical or electronic control.

5. Storage devices:

The function of memory in digital camera is to store digital image data, just like film recording optical signals, except that the image data in memory can be recorded and deleted repeatedly, while film can only record it once. Memory can be divided into built-in memory and mobile storage. Built-in memory is a kind of semiconductor memory, which is installed inside the camera and used to temporarily store images. When transmitting an image to a computer, it must pass through an interface such as a serial port. Its disadvantage is that the image file should be transferred to the computer in time after it is full, otherwise the image data cannot be stored in it. Most of the early digital cameras used built-in memory, while the newly developed digital cameras used mobile storage more. These removable memories can be 3.5-inch floppy disks, PC(PCMCIA) cards, CompactFlash cards, SmartMedia cards, etc. These memories are easy to use and can be taken out and replaced after shooting, which can reduce the manufacturing cost of digital cameras, increase the flexibility of application and improve the continuous shooting performance. The number of images stored in the memory depends on the memory capacity (MB), image quality and image file size (KB). The higher the image quality, the larger the image file and the larger the storage space required. Obviously, the larger the capacity of the memory, the more images can be saved. Generally speaking, a digital camera can store 10 to 200 pictures. Here we introduce some common storage schemes:

Smart media card,

From 2 megabytes to 32 megabytes, it is the most common digital camera memory card. Because there is no built-in control part, the cost is the lowest, but it can't break through the limit of 64 megabytes for the time being, but there may be 64 megabytes of cards launched this year. At present, most digital cameras use SM cards, and the speed is similar to other storage methods. In fact, the kernel is FlashMemory. Common digital camera support brands, Olympus, Fuji, Toshiba and many other brands. In addition, because MP3 players also need memory cards, SM cards are also selected due to cost problems, which leads to an increase in demand for SM, so its price drops rapidly due to mass production, and it is the best cost-effective storage scheme at present.

Compact flash memory card,

There are CF 1 and CF2 formats respectively, just like SM cards. The difference between the two is that it has its own control module, and it is much thicker. At the same time, it also supports other storage modes besides FlashMemory. The main storage sizes are 4, 8, 15, 30, 40, 64, 96, 128, 224, 400 and so on. Among them, those larger than 128 must use CF2 format. At present, Kodak, Casio, Nikon, Canon and other digital cameras all use CF cards.

IBM's MicroDrive,

What is IBM's MicroDrive? IBM's MicroDrive is an excellent storage solution specially prepared by IBM for digital cameras. CF2 interface is adopted, which is compatible with CF2 memory card. It can be used in digital cameras that can be inserted into CF2 memory cards. At the same time, it has PC card interface, and can also be used in professional digital cameras that support PC card interface. Its capacity is 340 megabytes; In addition, because it is a hard disk, its speed is also very fast, and the speed of FlashMemory is not comparable to that of a hard disk. Therefore, in addition to the large capacity, the speed is much faster than that of CF card, and the price is similar to that of 128 MB CF card.

Click:

Iomega, a famous company that produces mobile storage devices, has introduced a unique disk. This small disk, which is not much bigger than CF card, can store 40MB of data, but the cost is much lower than that of products using flash memory technology. Moreover, Click can be accessed through a computer.

Memory stick:

Sony's storage device is about half the size of a piece of chewing gum. It has been widely supported in Sony's full range of products, with a capacity of 64MB. In order to further expand its application scope, Sony's digital camera using floppy disk can also save data on it through converter.

6.LCD (liquid crystal display):

LCD (Liquid Crystal Display) is a kind of liquid crystal display. The LCD used in a digital camera works on the same principle as the LCD of a notebook computer, but its size is smaller. In terms of types, liquid crystal displays can be roughly divided into two categories, namely DSTN-LCD (Double Scan Twisted Nematic Liquid Crystal Display) and TFT-LCD (Thin Film Transistor Liquid Crystal Display). Compared with DSTN, TFT is characterized by high brightness and can get clear pictures from all angles, so TFT-LCD is mostly used in digital cameras. LCD has three functions, one is framing, the other is displaying, and the third is displaying function menu.

7. Output interface:

The output interface of digital camera mainly includes computer communication interface, video interface connected to TV set and interface connected to printer. Commonly used computer communication interfaces include serial interface, parallel interface, USB interface and SCSI interface. If infrared data association is used, the corresponding infrared receiver and its driver should be installed for the computer. If your digital camera has a PCMCIA memory card, you can insert the memory card directly into the PC card slot of your laptop. Floppy disk is the most common and economical storage medium, and some digital cameras use floppy disk as storage medium. Take out the floppy disk directly from the digital camera, insert it into the computer floppy drive, and transfer the image file to the computer.