Why can a virtual image made of a mirror be photographed by a camera in front of the mirror?

Digital cameras use electronic components to image rather than film-this is the most essential difference between digital cameras and traditional cameras. Imaging devices of digital cameras are mainly divided into two categories:

CCD-abbreviation of English Charge Coupled Device, Chinese name is "Charge Coupled Device".

Cmos-abbreviation of English complementary metal-oxide semiconductor, Chinese name is "complementary metal-oxide semiconductor".

2. 1)CCD is the mainstream imaging device at present, which is mainly divided into:

(1)R-G-B primary CCD: This is the most widely used CCD in digital cameras.

(2)C-Y-G-M complementary color CCD: Some Nikon digital cameras used this complementary color CCD earlier.

(3)R-G-B-E four-color CCD: This is the latest CCD released by Sony, which has one more E (Emerald) color than RGB primary CCD.

2) Super CCD: It is a patented technology of Fuji Company in Japan. Its Chinese name is Super CCD, which evolved from CCD and has now developed to the fourth generation.

3)CMOS: As an imaging device of digital camera, it has not appeared for a long time, but it has developed very rapidly and is likely to compete with CCD. There is no essential difference between the pixel arrangement in its basic structure and the R-G-B primary color CCD. Canon is the main supporter of the CMO camp.

3. How does a digital camera image?

A) light is projected onto the surface layer of a photosensitive element through a lens;

B) the light is decomposed into different colors by the surface filter of the photosensitive element;

C) The colored light is induced by the photosensitive unit corresponding to each filter to generate analog current signals with different intensities, and then these signals are collected by the circuit of the photosensitive element;

D) Analog signals are converted into digital signals by digital-to-analog converters, and then these signals are processed by DSP and restored into digital images;

E) transmitting the digital image to a memory card for storage.

4. What are the characteristics of 4.CCD?

The CCD technology is mature and the imaging quality is good. After all, it is the most widely used imaging element now, but it also has shortcomings:

1) consumes a lot of power. Early digital cameras were known as "electric tigers", and one of the main reasons came from CCD. Although the use of low-energy components such as low-temperature polysilicon display screen reduces the power consumption of the camera to a certain extent, CCD is still a big power consumer of digital cameras-CCD keeps working at any time after the digital camera is turned on, which consumes a lot of electricity unnecessarily.

2) The process is complicated and the cost is high. The complex structure of CCD determines the complexity of its manufacturing process, so so far, only a few electronic giants can produce CCD.

3) pixel promotion is difficult. The first two shortcomings of CCD also directly lead to this shortcoming. There are only two ways to improve CCD pixels: one is to increase the CCD area by keeping the unit area of photosensitive elements unchanged, and integrate more photosensitive elements on a large CCD. However, this method will lead to low yield of CCD, high manufacturing cost and high power consumption, which is unrealistic in the civil field; Second, reduce the unit area of photosensitive elements and integrate more photosensitive elements on the existing horizontal CCD area. However, this method will reduce the unit photosensitive area of photosensitive elements, reduce the overall sensitivity and dynamic range of CCD and affect the image quality.

5. What are the characteristics of 5.CMOS?

In recent years, the development speed of CMOS is quite good, and it has great potential to compete with CCD-even the top DSLR (Single Lens Reflective Digital Camera), Kodak DCS/KOOC-0/4N and Canon EOS/KOOC-0/DS all use CMOS imaging.

Compared with CCD, CMOS has two outstanding advantages:

1) has low price and simple manufacturing process. CMOS can be produced by ordinary semiconductor production line, unlike CCD, which requires special production process, so the manufacturing cost is much lower. Moreover, the size and output of CMOS are not as limited as CCD.

2) Low power consumption. Although there is little difference between CMOS filter layout and CCD, the circuit structure of photosensitive unit is very different. Each photosensitive element of CMOS has an independent charge/voltage conversion circuit, which can independently amplify and output the electrical signal after photoelectric conversion-this is much faster than CCD collecting all the signals and then amplifying the output. Moreover, the photosensitive element of CMOS only works during photosensitive imaging, so it saves electricity compared with CCD. However, CMOS also has disadvantages. If there are many imaging actions when using a digital camera, CMOS will heat up due to the changeable current when it is started frequently, which will lead to disorder and affect the image quality.

6. How to understand the basic parameters of imaging elements?

Imaging element is the core of digital camera, so it is necessary to know some important parameters correctly, which will bring a lot of help to understand the basic performance of digital camera and how to buy digital camera.

Total pixels-Total pixels refer to the number of imaging units on the imaging element of a digital camera. A CCD with a total pixel of 5.24 million means that 5.24 million imaging units are integrated on it. The total number of pixels is basically used to mark the performance of digital codes one by one.

Effective pixel-When a digital camera is imaging, the edge of the photosensitive element will be blurred due to the diffraction of light. In order to ensure the imaging quality, this part of the imaging on the photosensitive element will be discarded, so the photosensitive unit cannot use 100%. The utilized pixel, that is, the final image, becomes an effective pixel.

Size-refers to the diagonal length of the photosensitive element, usually in inches. Common ones are11.8 inch, 1/2.7 inch, 2/3 inch and so on. Generally speaking, the larger the size of the photosensitive element, the better the performance and imaging effect of the element. In addition, the photosensitive elements of digital cameras generally adopt the aspect ratio of 4: 3, especially 3: 2.

ISO- refers to the sensitivity of photosensitive elements to light induction. The larger the value, the higher the sensitivity. Common values are 50, 80, 100, 160, 200, 400, etc. At present, the highest ISO value of photosensitive elements of digital cameras can reach 3200. It should be noted that although a high ISO value can improve the imaging quality of a digital camera in a dark environment, the higher the ISO value, the more obvious the impact on the image quality and the more noise there will be.

In layman's terms,

Before understanding the characteristics and basic components of digital cameras, we should first understand the working principle of digital cameras, which is conducive to better understanding and mastering the key parameters of cameras and in-depth understanding of camera performance.

When the power switch of the camera is turned on, the main control program chip begins to check the whole camera to determine whether the components are in working condition. If everything is all right, the camera will be on standby at any time; If a component fails, an error message will be displayed on the LCD screen and the camera will stop working completely.

When the user aims at the shooting target and presses the shutter half-way, the microprocessor in the camera starts to work to determine the focal length, shutter speed and aperture size. When the shutter is pressed, the optical lens can focus the light on the image sensor. This CCD/CMOS semiconductor device replaces the position of the film in the traditional camera, and it can convert the captured scene light signal into an electrical signal.

At this time, an electronic image corresponding to the shooting scene is obtained. Because the image file is still an analog signal and cannot be recognized by the computer, it needs to be converted into a digital signal by an A/D (analog/digital converter) before it can be stored as data. Then, the microprocessor compresses the digital signal and converts it into a specific image format. Commonly used file formats for describing two-dimensional images are Tag TIFF (image file format), RAW (original data format), FPX(Flash Pix), JFIF(JPEG file exchange format) and so on. Finally, the image file with digital signal will be stored in the built-in memory in the specified format, and then a digital photo will be taken. At this time, the photographed photos can be viewed through the LCD (Liquid Crystal Display).

The general process is briefly introduced in the front, and the whole process of photo imaging will be described in detail with reference to Figure 1- 1.

(1) When shooting a scene with a digital camera, the light reflected from the scene is transmitted to a CD through the lens of the digital camera.

(2) When the CCD is exposed to light, the photodiode is excited by light, releasing charges and generating electrical signals of photosensitive elements.

(The CCD control chip uses the control signal circuit in the photosensitive element to control the current generated by the light-emitting diode, which is output by the current transmission circuit. The CCD will collect the electrical signal generated by one imaging and output it to the amplifier.

(4) The amplified and filtered electrical signals are transmitted to ADC, which converts the electrical signals (analog signals) into digital signals. The magnitude of numerical values and the intensity of electrical signals are directly proportional to the voltage, and these numerical values are actually image data.

(5) At this time, these image data can not directly generate images, but should be output to DSP (Digital Signal Processor). In DSP, these image data will be processed by color correction and white balance, and encoded into image formats and resolutions supported by digital cameras, and then stored as image files.

(6) When the above steps are completed, the image file will be saved in the memory, and we can enjoy it.