In the years of camera development, from the initial vacuum tube camera to the current CCD, CMOS, DPS cameras, with the continuous development of camera applications, a variety of dedicated camera technology has emerged, and wide dynamic technology is one of them. For some special environments with strong contrast between light and dark, the balance adjustment ability of ordinary cameras for the most "dark" and "bright" parts of images is very limited, and wide dynamic technology can play its prominent role.
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DPS wide dynamic technology
In the case of backlighting, an ultra-wide dynamic camera is generally used. The dynamic range of the ultra-wide dynamic camera indicates the most "dark" and "bright" adjustment range of the image of the camera. The larger the dynamic range, the more the image is represented by the image. Rich and clear, of course, the color space of the image is wider, that is, the ability of the ultra-wide dynamic camera to adapt to the backlight environment is also greater.
Conventional CCD cameras only sample the entire image once during the acquisition of an image, so there is inevitably a phenomenon of overexposure of a bright area or a dark area of ​​the entire image.
Although the wide dynamic CCD camera has a breakthrough in technology compared with the traditional CCD camera, it has now developed into the third generation CCD wide dynamic camera, and the wide dynamic range has reached 160 times, or 54 dB. However, some data reveal that the dynamic range of CCD wide dynamic cameras can only reach 60dB at most. Now available CMOS-based DPS technology wide dynamic camera, its wide dynamic range is generally 95dB, up to 120dB.
The main feature of DPS technology is that it performs multiple independent lossless sampling for each pixel, which increases the dynamic range. It is said that wide dynamic imaging is to use multiple exposure technology to balance and adjust the brightness and dark image to restore the realistic effect of the realistic scene.
DPS (Digital Pixel System) is a digital image sensing processing system. Its core technology is to include an ADC (analong-to-digited digital-to-analog converter) on each pixel picked up. When the ADC captures the optical signal, it It is directly converted into a digital signal and amplified, which minimizes the inefficient transmission operation, reduces noise, and ensures high quality of the acquired image, so that the output image does not have any tailing and blooming. The DPS system is a truly pure digital image sensing system in the acquisition, transmission and processing of the entire image, regardless of whether the front-end pick-up or the back-end processing is performed in a digital form.
Based on the technological development of Stanford University in the 1990s, Pixim developed a new DPS image picking system that can obtain high quality images through its powerful wide dynamic function. Pixim's DPS imaging technology from Stanford University applied for 56 patents, 42 of which have already taken effect. Pixim's DPS technology is currently the only image capture system that directly represents optical signals in digital values. The CCD and CMOS sensors represent the optical signal with analog values ​​and then convert the analog values ​​to digital values. DPS does not have analog readout noise.
In DPS technology, each pixel has an ADC, and each pixel information is independently captured and processed. At the same time, a 32-bit CPU processing chip ARM7 (or ARM9) is used to control the exposure time of each pixel, so that the mode is - The number conversion is more precise. The sensor can sample the light of each pixel multiple times and at high speed during the exposure period, and control the exposure time of each pixel, and store the pixel information when it reaches the optimal state, so each pixel has passed many times (0.8 Within ms) no destructive separate sampling. After the pixels are acquired, the system processes them to form a high quality image. The image formed by the DPS system is consistent in horizontal and vertical resolution, ensuring high resolution of the image at any angle.
Pixim's patented DPS technology marks a fundamental breakthrough in camera technology. Cameras with CCD as the mainstream technology will be greatly affected by DPS technology.
DPS technology has good image quality and high image quality in the concept of reduction. DPS technology can make the exposure time of each pixel different, so that the exposure time of different parts of the same picture is different. Therefore, any point of the entire image can achieve the best image display state, can get clear image details, closer to the color reproduction of the real scene.
According to Pixim, "Every pixel is a camera" in DPS technology, in an image, there are hundreds of thousands of exposure pixels, even under the most harsh lighting conditions. Capture sharp, true-to-life images without ever being dark or destroyed by shadows, glare, reflections, and sunlight. Therefore, in DPS technology, the light corresponding to each pixel can be optimally exposed to form a high quality image.
The DPS camera uses the same working mode as the "human eye-brain" system, giving the image sensor and image processor a two-way real-time interaction. The process of ingesting and processing the image of the DPS camera is similar to the relationship between the human eye and the brain. While processing and computing the image, the instruction is continuously sent to the image sensor, which not only adjusts the exposure time, but also changes the actual image capture algorithm. Intelligent image processing.
Therefore, under certain image features and illumination, the DPS camera will eventually provide more detailed, complete and realistic image detail for optimal image quality.
DPS wide dynamic technology features
From the previous explanation, it can be known that wide dynamic technology is applied in a strong environment of light and dark intersections. It can also be understood as two environments, one is overexposure and the other is overly dark, such as in indoor and outdoor cross environment, camera installation Indoors, to make the indoor and outdoor two different environments clear, you must use wide dynamic technology to achieve the effect of reducing the image.
In addition to the same high definition as the CCD camera, the DPS camera fully reflects the outstanding features of the DPS camera in terms of chromaticity, white balance, contour compensation, and vertical spot. With its own OSD, you can set multiple functions and adjust multiple parameters to ensure monitoring needs in a variety of situations. Here are a few key features of the DPS camera:
1, the minimum illumination
1 Lux/F1.4 (AGC ON 50 IRE), 0.75 Lux/F 1.2 (AGC ON 50 IRE), 0.01 Lux/F 1.2 (maximum electronic sensitivity increase of 32 times).
2, WDR wide dynamic range
Typical value is 95dB, maximum value is 120dB, 36 adjustment level.
3, backlight compensation
The backlight compensation has the following four options.
·OFF, no backlight compensation is set;
· ON, usually full range backlight compensation;
· 1SPOT, 1 area backlight compensation, the size and position of the backlight compensation area can be selected by setting;
· 2SPOT, 2 area backlight compensation, the size and position of 2 backlight compensation areas can be selected by setting.
4, GAIN gain
When SENS UP ON is selected, there are two gain modes of AGC and HYP AGC. The following five gain modes are available when SENS UP OFF is selected.
· AGC mode is the initial automatic optimization of sensitivity and noise level;
· The sensitivity of the HYP AGC mode is higher than the AGC mode, but the image has noise points when the sensitivity is high and the light is dim;
· LOW is low, this low fixed mode sensitivity is lower than the brighter scene;
· In MID, this medium fixed mode sensitivity is between LOW low and HIGH;
HIGH is high, this high fixed mode sensitivity is used for darker scenes and maintains high sensitivity.
5. Five SENS UP sensitivity boost modes.
·OFF, there is no sensitivity increase in the initial mode;
·S/N, SNR mode is used to capture scenes with small moving range and brightness changes;
· STD, this standard mode can suppress image blur and roughness when shooting scenes with varying light;
· MOVE sport mode is used for scenes such as neighborhoods or parking lots with light changes and character movements;
· SLOW SHUTTER slow shutter electronic sensitivity, there are five options for ×2, ×4, ×8, ×16, ×32.
6, four automatic white balance adjustment mode.
· ATW, the initial setting is automatically adjusted;
· ATW Ex, when the color temperature range is higher than the ATW mode, under the normal light source, it is slightly faded compared with the ATW mode;
· AWC, this is the so-called ONE PUSH automatic white balance mode, using a white target as a reference to automatically adjust the white balance;
• MANUAL manually adjusts R red gain and B blue gain. After determining the monitoring scene and target, choose an optimal white balance mode to ensure the best color.
7. In terms of color adjustment, broadcast-level technology is applied to surveillance cameras.
· COLOR BAR itself has a color bar display function to assist in adjusting the color to ensure the best color;
· CHROMA chromaticity compensation adjustment to adjust the color of the image;
· DETAIL contour detail adjustment.
The emergence of wide dynamic technology makes up for the shortcomings of ordinary cameras in the intersection of light and dark, but there are also shortcomings. After all, wide dynamic technology is a special function for a specific environment. Cameras with a large dynamic range are often less sensitive, and high-sensitivity cameras have a relatively low dynamic range. That is to say, the current wide dynamic camera can fully meet the needs of the environment when the ambient light is sufficient, and presents a high quality image, but the use condition is not ideal under low illumination conditions, and the noise is too large. In the case of low illumination at night, the image will appear similar to the snowflake point. Sometimes other phenomena may occur. For example, it is normal to just install and debug. After a period of time, the screen will have a color cast. This phenomenon is related to the influence of the environment or the setting of the camera itself. Generally, the wide dynamic camera has a color cast. It is related to white balance. If it is set to automatically track white balance image when debugging, it will produce different white balance effect with the change of environment, and adjust white balance mode to automatic white balance. In addition, the position of the installation during the installation process also has a deviation from the image. The position of the reflection point of the glare should be avoided as much as possible. These are all matters needing attention in the installation and debugging of the wide dynamic camera.
DPS wide dynamic technology application
The excellent wide dynamic function allows the DPS camera to see the details of every corner of the panorama in a high contrast light environment (especially when looking outdoors), such as an office building lobby with large glass windows, a bank, an ATM machine. , shops, airports, etc., these are scenes with bright background light at the door, window, etc. In the road traffic system, the license plate can be seen by using the wide dynamic function of the DPS camera to achieve the strong light suppression effect. Use the wide dynamics of the DPS camera (which suppresses glare and reduces the halo of the light source) and the extremely wide color temperature range (even if the original color of the image can be saved even in different lighting conditions), you can also use the camera Look at the vehicle violations in the street monitoring system.
Conclusion
With the overall digital development trend of surveillance systems, the digital development of camera products has become an inevitable trend. As a new technology implementation, in the future development of camera technology, cameras with CCD as the mainstream technology will be greatly affected by DPS technology. With the continuous improvement of camera technology, the shortcomings of various imaging technologies will also Solve the solution.
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