With the release of the small drone Mavic at the end of last month, the entire UAV industry officially entered the trend of miniaturization. However, in order to lead the industry under this emerging trend, efforts to analyze the important technologies in miniaturized drones must be one of the information that practitioners need to pay special attention to.
In this issue of intelligent internal reference, we recommend a small drone report from GF Securities, first throwing an important conclusion to enjoy the fun: miniaturization is a trend, but the gimbal can not be easily matched.
The reason for this will be answered in the text. The following are the dry goods presented by the smart internal reference:
Technical points are = " aerial photography" + "unmanned aerial vehicle"Small UAV products on the market need to focus on hovering positioning technology, obstacle avoidance technology, visual follow-up, and image transmission technology. The picture below shows a comprehensive comparison of Davic Mavic and its class products.
To sort out the aerial photography technology of drones, you first need to know what points of aerial photography technology for drones. Generally speaking, the aerial photography technology of the drone can be split into two points simply by literally "unmanned aerial vehicle" + " aerial photography":
(1) Image capture technology, ie imaging and image processing technology;
(2) UAV platform technology, mainly refers to the fuselage control technology that provides a stable aerial photography environment for aerial photography.
Image capture technology: The current image capture solutions on the market are integrated applications of mainstream camera modules of several major brands. UAV manufacturers do not have much technical space in this respect, and because technology development has been compared Mature, the gap between different product plans is not large. Therefore, this report is only a brief introduction.
Unmanned aerial platform stability technology: refers to the technology related to the UAV's own flight technology in addition to flight navigation, control and other unmanned aerial vehicles. This technique is the most critical factor affecting image quality.
With the rapid development of smart phones in recent years, the technology related to smart phones has been unprecedentedly developed. The hardware technology of smart phone cores highlighted by touch screens, processors and camera modules is the basis of large-scale industrialization needs. On the basis of low power consumption, high performance and high integration, the company has eliminated a large number of backward technology production capacity in this industrial development process, and the products are continuously concentrated to giant companies such as Sony and Samsung.
It can be seen that regardless of sales or sales, Sony has firmly topped the list with its outstanding performance in the mobile market. From the perspective of total brand distribution, the top 4 companies accounted for nearly 75% of the market share, and the market distribution is relatively concentrated.
Parameters affecting imaging qualityIn terms of the technical parameters that reflect the imaging level of a single camera module, usually everyone is concerned about specific, apparent parameters, such as the number of pixels, aperture size, etc., but there are many parameters affecting the imaging quality on the camera module: single pixel Size, sensor technology, lens group technology, ISP technology, etc. Let's make a brief introduction below.
Pixels/resolution: pixels such as 8 megapixels (3200&TImes; 2400 resolution), 13 million pixels (4208 & TImes; 3120 resolution) are the most frequently mentioned concepts in camera module technology, but the number of pixels is not The decisive factor in determining image clarity. The number of pixels only determines how many unit pixels are in an image, that is, the degree of detail that the image can show after zooming in, but the quality of each detail and the entire photo depends on many other factors.
As for the relatively hot "4K video recording" concept, it refers to the resolution of 4096 & TImes; 2160 image capture capability, in fact, the 4K update trend mainly comes from the playback device and film capture equipment, because the previous playback device HD standard is 1920 & TImes; 1080 resolution, the current 4K pixel level is four times the previous level, facing many challenges. Similarly, film shooting will be upgraded from the original ear 35mm film to 70mm, facing the upgrade of industry-standard equipment. However, the 4K resolution digital video capture capability only requires the sensor to reach 1200w pixels, and the image processing capability that can be matched with it. This industry has mature supporting solutions (such as Qualcomm's Snapdragon Flight platform not only supports 4K recording, but also Support 4K stereo VGA recording), therefore, does not constitute a technical barrier.
Aperture size: The size of the aperture directly affects the amount of light, which has a great impact on the image quality. At present, the camera module of mobile consumer electronics has gradually increased from f/2.4, f/2.2, f/2.0 (the number is higher Small, the larger the aperture), the mobile phone market has also begun to appear f/1.8 camera module in large areas.
Aperture enlargement has two main advantages for shooting imaging: 1. Improve image quality under low light; 2. Increase shutter speed; 3. Reduce depth of field.
For aerial photography applications, it is necessary to improve the image quality under low light (night scene shooting) and increase the shutter speed (motion shooting), while reducing the depth of field can better blur the background during portrait shooting, highlighting the subject This kind of demand is a icing on the cake for the drones that are currently used for the purpose of shooting large objects, but it is necessary for self-timer drones. For example, the main self-timer Dobby drone uses the f/1.8 aperture, while the Dajiang 4 uses the f/2.8 aperture.
However, from the perspective of the current industry technology level and product strategy, the improvement of aperture is not without cost:
1) After the amount of light entering the large aperture is increased, the first thing that needs to be improved is the shutter speed. In the dark environment, the original light is weak, and the shutter speed does not need to be increased much to ensure the quality of shooting. However, in the daytime or in a strong light environment, considering that the drone or mobile electronic device usually uses a fixed aperture and cannot adjust to a suitable small aperture, it is necessary to increase the shutter speed to avoid overexposure, but From the current technical level, there are still some technical bottlenecks in the improvement of the shutter speed, which is also an important factor that restricts the increase of the aperture on the miniaturized device.
2), the aperture increase also causes image distortion and edge quality degradation. In order to correct the degradation of edge quality and image distortion, more lens groups and the mechanical structure of the lens portion are usually used, which is difficult for small devices (such as iphone6 ​​and later devices in order to achieve f/1.8 aperture). And related to some other technical considerations, the camera height is increased, and is much higher than the fuselage, protruding from the outside). Of course, the consideration of miniaturization is not a particularly big problem on drones, but there may be certain thresholds for technology implementation.
Sensor technology: sensor technology is currently mainly Sony, OmniVision, Samsung, and Sony, especially the company's IMX220/230/240 series of sensors account for almost half of the marketed mobile phones, Apple, Samsung, Sony, Huawei The popular flagship machines such as Xiaomi and Meizu are almost all IMX series sensors. Therefore, the application on the drone only needs to select the corresponding product according to the drone's pricing strategy. Sensor technology mainly involves two parts of the sensor size and sensor structure.
ISP technology: ISP (Image Signal Processing) is also the image processing technology. The lens and sensor constitute the image receiving device, while the ISP constitutes the image acquisition and preprocessing. In the face of the current high-definition full-size high frame rate The data throughput requirements, ISP technology is also constantly improving. In addition to high-speed shooting and noise suppression, the camera can also make significant adjustments to the image with the help of the ISP processor. HDR technology is an obvious example.
HDR technology is a major application of ISP technology. It can continuously take several photos by adopting different exposure strategies, and synthesize several photos through ISP processor, retaining the details of dark parts and highlights, greatly enhancing the level of the picture. Feeling, if this synthesis algorithm is completed by the mobile phone's own processor, it will inevitably increase the processor burden, and considering the particularity of image processing, the effect may not be perfect, so many manufacturers have set up independent ISP processors, specifically Preprocess the photo. It is also possible to make adjustments to the overall rendering effect of the screen by ISP technology, and different vendors have different tendencies.
Autofocus technology is also a major feature of ISPs. At present, there are three main types of autofocus modes: contrast focus, phase focus, and laser focus. These three focusing methods, especially contrast focusing, require panoramic scanning of the image, and the ISP resource consumption is huge; phase focusing also requires real-time processing of the image, although the calculation amount is small, but the speed requirement is high, and the ISP has the same ability. Claim.
Therefore, regardless of the imaging look and feel, the use of autofocus shooting, etc., ISP technology has a greater impact on shooting imaging.
It can be seen from the above analysis that there are many factors affecting the final image quality, and it is difficult to improve the overall level by a single adjustment parameter. Therefore, the design of the camera module is a core technical field that is quite a test of the industrial design level, from the current status quo. In view of this, domestic UAV manufacturers are still relatively early in their exploration of this field. However, it must be noted that the current development of camera module technology is indeed quite mature in a certain sense. Most of the improvement of imaging technology in the professional field can show differences. For the average consumer, the improvement of the use experience is not obvious, and the imaging technology should be weaker for the final image quality improvement marginal effect.
We believe that imaging technology is important, but according to the current maturity and improvement potential, the stability technology focused on the UAV shooting platform is more obvious than the imaging technology.
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