High-Definition Mega Pixel HD Lens Four Main Structures

High-Definition Mega Pixel CCTV LENS MEGA PIXEL BOARD LEN

High-Definition Mega Pixel HD Lens Four Main Structures

What kind of lens is the HD lens?
 
For high-definition cameras, it can be equipped with a common lens called megapixel, or with a million high-definition lens, or with a 3 million high-definition lens. In the case of the same camera, the final performance of the picture, the resolution of the lens A decisive role.
 
According to the technical indicators published by some products, the general “megapixel lens” has a central portion of the resolution of only 1 million pixels, and the periphery will be attenuated to only 500,000 to 600,000 pixels. At present, the mainstream “megapixel high-definition” lens on the market, the published technical indicators are usually 70% of the field height as the radius of the imaging circle, the resolution of 3 million pixels, 70% of the field height of the imaging circle can reach the resolution More than 1 million pixels.
 
Nowadays, only a very small number of “HD” lens products can be achieved: 80% of the field height is the radius of the imaging circle, the resolution is 3 million pixels, and the resolution around the image circle of 80% of the field height remains. More than 2 million pixels. Therefore, it is not difficult to see that due to the huge price difference between the high-definition lens and the ordinary lens, there are more and more definitions of the concept of confusion in the market, which makes consumers look at the fog. However, after the veil of these “beautiful” is removed, the high price is not necessarily the high quality product.
 
Nowadays, with the development and maturity of high-definition cameras, high-definition monitors, network transmission and other technologies, the CCTV security market is also entering the high-definition era. In such a wave of technological upgrading, the lens should not become a stumbling block for the high-definition development of the CCTV market. Therefore, the clear and unified “high-definition lens” indicator has become a top priority nowadays.
 

Identify the four main points of HD lens

It seems that as long as the monitoring system is mentioned, what people immediately think of is HD. So can HD monitoring really bring us a high-definition experience? Lenses that play a key role in the imaging process, and those that are easy to ignore? Please look down.

 
First, the lens is the key to using ED lenses

 
In the commonly used security surveillance market, we use more fixed-focus or manual zoom lenses, because the monitoring distance is closer, and the lens focal length is generally less than 50mm. This kind of scene has almost no requirement for the anti-dispersion performance of the lens. However, once a motorized zoom lens is used to monitor distant targets, the dispersion problem is highlighted (dispersion is the shift of the light of various wavelengths in visible light after being refracted by the lens, and the image is blue on the edge of the object. Color or red color strip). Originally in the analog monitoring system, due to the large size of the pixel, the problem of dispersion is not very prominent, and it will only be manifested when the 300mm focal length is configured. In the high-definition era, the commonly used 120mm focal length motorized zoom lens has been more obvious to see this problem. This has higher requirements on the lens in terms of material and coating accuracy. The higher the clarity of the matched camera, the more obvious the effect of the lens material on the imaging effect.
 
Second, large diameter design is the key
 
So is it possible to completely solve the problem of remote monitoring with the lens of ED lens? Usually we turn the image of 720p or more sharpness into a high-definition image. According to the free choice of the market, most of them use the 1080p output format. In the field of remote monitoring, users want to use high-definition surveillance systems to improve the pixels of the picture, so as to more clearly view long-distance targets. According to our actual experience, watching in HD system not only does not make the picture sharpness, but the color reproduction ability and sharpness of the picture are greatly attenuated. The sharpness of the output image is even worse than that of D1, even worse than the analog camera. .
 
When the focal length is elongated, the picture becomes a black and white picture, the sharpness is seriously degraded, and the image effect is worse than that of the same lens with the Hitachi ultra-low illumination camera. It is not difficult to understand this situation. Most of the HD cameras we use now use CMOS chips, and the illumination performance can only reach 0.5Lux. In the process of the focal length change of the telephoto lens, the luminous flux will also change, and the longer the focal length, the worse the luminous flux. When the focal length is extended to the maximum, the luminous flux is reduced to the weakest. Although it is daytime, for the camera, it is equivalent to being blocked in front, leaving only a small hole to transmit light. In this case, the normal high-definition camera will have a picture quality degradation due to insufficient illumination. To solve this problem, we can start from two aspects:
 
1. Adopt high-definition camera designed for long-distance monitoring. For example, high-definition SDI cameras, in addition to the minimum illumination of 0.3Lux, also added color reproduction and low illumination image enhancement technology for remote monitoring. This allows a clear picture to be obtained when the luminous flux is lowered.
 
2. Improve the luminous flux of the lens when the focal length is elongated. Once the lens is produced, the range of luminous flux is determined and cannot be changed. Therefore, we must select those products with better luminous flux performance at long focal lengths when selecting lenses. According to the optical relationship of the lens, F (inverse ratio of luminous flux) = f (focal length) / D (effective aperture before the lens). The F value is the inverse ratio of the luminous flux. The smaller the value, the better the luminous flux performance. Then, in the case of the same f, the lens with the larger effective aperture is selected, and the obtained picture effect is better.
 
Third, the IR function is easily overlooked
 
Users pay attention to high-definition systems, not only pay attention to whether they can get clear pictures during the day, but also monitor performance at night. In high-definition systems, IR functions are generally forgotten. However, with the improvement of the photographic performance of the high-definition system, the IR function is gradually recognized by users in the all-weather monitoring system. Especially for the power zoom system, the IR function is crucial. For systems with auxiliary light sources such as laser illuminators, the availability of IR functions will directly affect the ease of use and usability of the system.
 
Fourth, the large target design has a high degree of adaptability to the camera
 
In order to improve the picture performance, high-definition products often use a large-sized sensor chip. Often these cameras encounter a lot of confusion when configuring the lens. The lens produced by most lens manufacturers still uses the dimensional standards of the past analog era, namely 1/2″ and 1/3″ products. The actual specifications of the cameras on the market are mostly the following two:
 
1. Use products larger than 1/3″ and less than 1/2″, such as 1/2.5″, 1/2.7″, 1/2.8″. These cameras use 1/3″ lens when configuring HD lens. Will cause the picture to produce a “dark corner”. Therefore, the current 1/3″ high-definition lens, especially the motorized zoom lens, has almost become a chicken rib. In this application, the user uses 1/2″ or more. For example, KOWA’s 7.5-127mm product.
 
2. Use products larger than 1/2″, such as 1/1.8″, 2/3″. Cameras with 1/1.8″ sensor chip are more or less 1/2″ when configuring HD lens. Vignetting may occur, so the customer chooses to use a 1/1.8″ mirror’ head as much as possible. This will ensure that there will be no vignetting. For specifications larger than 1/1.8″, you should choose products with 2/3″ or 1″ specifications.
 
In short, for high-definition imaging systems, there are many technical details that are not worthy of attention compared to mature analog monitoring systems. The details determine success or failure, and excellent imaging systems will consider more. With the gradual popularization of high-definition systems, the choice of high-definition lenses will be more rational, and with the strong demand, it will in turn promote the continuous upgrading and development of products.

High-Definition Mega Pixel HD Lens by SGCCTV Choicecycle Singapore.

Sim Lim Square 02-81, 11~7pm daily. Whatsapp +65 98534404 [email protected] 

什么样的镜头才是高清镜头

  对高清摄像机而言,可以配用号称百万像素的普通镜头,也可以配百万高清镜头,更可以配300万高清镜头,而在相同摄像机情况下,画面最终的表现,镜头的分辨率起了决定性的作用。

  根据部分产品公布的技术指标来看,一般的“百万像素镜头”其中心部分解像力只有100万像素,而周边会衰减至仅50~60万像素。目前,市场上主流的“百万像素高清”镜头,公布的技术指标通常是场高的70%为半径的成像圆,解像力达到300万像素,场高70%的成像圆以外的部分可以达到解像力100万像素以上。

  现在市场上,仅有极少数的“高清”镜头产品能做到:在场高的80%为半径的成像圆,解像力达到300万像素,同时场高80%的成像圆周围的部分,解像力仍维持在200万像素以上。因而不难看出:由于高清镜头和普通镜头之间存在着巨大价差,因此市场上出现越来越多的混淆概念的镜头定义,使消费者雾里看花。但是将这些“美丽”的面纱揭去后,高价背后的不一定就是高质量的产品。

  如今,随着高清摄像机、高清监视器、网络传输等技术的发展和成熟,CCTV安防市场也正跨入了高清时代。在如此的技术升级换代的浪潮中,镜头不应成为CCTV市场高清发展的绊脚石,所以,明确统一的“高清镜头”指标成为时下的当务之急。

  识别高清镜头的四大要点

  似乎只要提到监控系统,让人立即想到的就是高清。那么高清监控真的能够带给我们高清的体验吗?在成像过程中起到关键作用的镜头,又有那些容易忽略的问题?请往下看。

  一、镜头采用ED镜片是关键

  常用的安防监控市场,我们更多地采用的是定焦或者手动变焦的镜头,因为监控距离较近,一般采用的镜头焦距在50mm以内。这种场景对镜头的防色散性能几乎没有要求。但一旦采用了电动变焦镜头来对较远目标的监控,色散问题就凸显出来(色散是可见光中的各种波长的光经过镜头折射后会出现焦点偏移,表现在图像上就是物体边缘有蓝色或者红色的色条)。原来在模拟监控系统,由于像元尺寸较大,色散的问题不是很突出,只有在配置300mm焦距以上的情况下才会表现出来。而进入高清时代,在常用的120mm焦距段的电动变焦镜头,已经比较明显的可以看到这个问题。这就在材质和镀膜精度上对镜头有了更高的要求。配合的摄像机清晰度越高,镜片材质对成像效果的影响越发明显。

  二、大口径设计是关键

  那么是不是采用ED镜片的镜头就能完全解决远距离监控的问题呢?通常我们把720p以上清晰度输出的图像成为高清图像。而根据市场的自由选择,大多采用的是1080p的输出格式。在远距离监控领域,用户希望用高清监控系统来提高画面的像素,进而更加清晰的观看远距离目标。而根据我们实际经验,采用高清系统观看,非但没有使得画面清晰度提成,反而画面的色彩还原能力、清晰度均大幅衰减,输出图像的清晰度比D1画质还要差,甚至还不如模拟摄像机。

  在焦距拉长时,画面变成了黑白画面,清晰度严重下降,图像效果比相同镜头配合日立超低照度摄像机的效果还要差。出现这种情况其实并不难理解。我们现在采用的高清摄像机大多采用的是CMOS芯片,照度性能只能达到0.5Lux。而长焦镜头在焦距变化的过程中,光通量也会随之变化,焦距越长,光通量越差。当焦距拉长到最大值时,光通量减到最弱。虽然是白天,但对于摄像机来说,相当于面前被遮挡,只留了很小的孔透过光。在这种情况下,普通高清摄像机就会因为照度不够出现画面质量衰减。解决这种问题可以从两方面入手:

  1、采用针对远距离监控设计的高清摄像机。例如高清SDI摄像机,这种摄像机除了最低照度做到0.3Lux的同时,还针对远距离监控领域加入了针对色彩还原和低照度图像增强技术。使得在光通量下降时也能得到清晰的画面。

  2、提高焦距拉长时镜头的光通量。镜头一旦生产出来,光通量的范围即确定下来,不可更改。因此我们必须在选择镜头时挑选那些长焦距时光通量性能较好的产品。根据镜头的光学关系,F(光通量的反比)=f(焦距)/D(镜头前有效口径)。F值是光通量反比,这个值越小,光通量性能越好。那么在f相同的情况下,选择有效口径越大的镜头,得到的画面效果越好。

  三、IR功能容易被忽视

  用户关注高清系统,不只是关注白天能否得到清晰的画面,夜晚的监控性能也是关注的要点。在高清系统里面,IR功能被普遍淡忘。但随着高清系统感光性能的提高,全天候监控系统中,IR功能逐渐得到用户的认可。尤其是电动变焦系统,IR功能至关重要。对于配合激光照明器等辅助光源的系统,IR功能是否具备,将直接影响到该系统的使用便捷性和可用性。

  四、大靶面设计对摄像机的适应程度高

  目前高清产品为了提高画面性能,往往采用大靶面的感光芯片。往往这些摄像机在配置镜头时,就会遇到许多困惑。大部分镜头厂商生产的镜头还是沿用过去模拟时代的尺寸标准,即1/2″和1/3″的产品。而市场上摄像机的规格实际情况多采用以下两种:

  1、采用大于1/3″而小于1/2″的产品,例如1/2.5″,1/2.7″,1/2.8″。这些摄像机在配置高清镜头时,如果采用1/3″镜头,将会使得画面产生“暗角”。因此目前1/3″的高清镜头尤其是电动变焦镜头几乎成了鸡肋。在这种应用中,用户采用的均是1/2″以上的产品。例如KOWA的7.5-127mm产品。

  2、采用大于1/2″的产品,例如1/1.8″,2/3″。采用1/1.8″感光芯片的摄像机在配置高清镜头时,如果采用1/2″的产品,或多或少可能会出现暗角的情况。因此客户选择配置时,尽量采用的是1/1.8″的镜’头。这样可以保证不至于出现暗角的情况。对于大于1/1.8″的规格,则应该选择2/3″或者1″等规格的产品。

  总之,对于高清成像系统,相对于成熟的模拟监控系统,还有很多不为人重视的技术细节。而细节决定成败,优秀的成像系统会考虑的更多。随着高清系统的逐渐普及,高清镜头的选择将更加理性,同时随着需求的旺盛,将反过来推动产品的不断升级、发展。