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七郎 / Seven Liu

科学与艺术,恰如人生中的红颜知己。 本博内容保留所有权利.

 
 
 

日志

 
 

4.11 Eccentricity and Radial Run-out 偏心距和径向跳动  

2012-06-27 11:15:20|  分类: 读点英文 |  标签: |举报 |字号 订阅

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The eccentricity (ECC) of a disc is defined as the distance between the center of the spiral track and the center of the inner hole of the disc. The left part of Figure 4.14 shows a disc (black circle) where the ideal track (blue circle) has no eccentricity, considered in this context as the reference. On the other hand, the red circle illustrates a spiral track which is eccentric with respect to the inner hole.

光盘的偏心距定义为盘片内孔中心与螺旋轨道几何中心之间的距离。在图4.14的左图上,盘片(黑色圆)上的理想轨道(蓝色圆)没有偏心,由此可将其看做参考基准,而红色圆表示相对于内孔偏心的螺旋轨道。

Given the case an eccentric disc rotates, the position of the track to follow travels from position A+ to position A- and back to position A+ for every revolution, see right part of Figure 4.14. In order to follow the track in question the radial servo must compensate for the eccentric disturbance and consequently the focus point describes a sinusoidal trajectory with amplitude |A|, which corresponds to the eccentricity of the disc. Such disturbance has a frequency content equal to the rotation frequency of the disc (fECC = frotation) .

如果将偏心的光盘旋转起来,每旋转一圈,轨道的位置都会从位置A+移动到A-然后再移回A+位置,参见图4.14的右图。为了对有问题的轨道进行跟踪,径向伺服必须补偿偏心的干扰,结果是聚焦点的运动轨迹呈振幅为|A|的正弦曲线,相当于盘片的偏心距。这种干扰的频率等于光盘的旋转频率(fECC = frotation)。

From the illustration above, it can be observed that the radial run out (RRO) is twice as large as the eccentricity. In practice, RRO can be larger because it is not defined with respect to the center of the inner hole of the disc but with respect to the ideal track to be read, where the ideal track has no eccentricity and is perfectly circular. Any local deviation of the track referred to as unroundness (out-of-roundness) contribute to RRO. Hence, RRO is defined as the peak-to-peak track deviation from the ideal track.

如上图所示,可观察到径向跳动(RRO)相当于两倍的偏心距(ECC)。实际上,RRO可能更大一点儿,因为RRO不是以内孔中心为基准定义的,而是以理想轨道为基准定义的。而理想轨道是没有偏心的完美的圆。轨道上任何的局部偏差,即不圆度,都会使径向跳动增大。因此,径向跳动(RRO)被定义为相对于理想轨道的轨道偏差的峰-峰值。

It is not guaranteed that an excessively high RRO can be compensated by the radial servo, especially at high reading speeds since the frequency of the disturbances are at least equal to the rotation frequency of the disc. RRO should therefore be within the described limits of the format specifications in order to unsure a certain playability level.

径向伺服无法保证可对过高的RRO进行补偿,尤其是在高速读取的时候,因为其干扰的频率太高,至少等于盘片旋转频率。因此,为保证盘片应有的可播放性,RRO应严格控制在BD规格书要求的限度之内。

In a replication plant, the most typical reason for a disc to be eccentric is the off-centered punch of the inner hole. In a dual layer disc, this process results in an equal eccentricity for both layers. Meanwhile an inadequate bonding may result in different eccentricities for both layers.

在复制工厂中,盘片偏心的原因大多是偏心了的内孔切刀造成的。而对双层盘片来说,对两层的影响是相同的。同时,不恰当的贴合也会对两层产生不同的影响。

 

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Key Words:

·eccentric 1. (人、举止或行为等)古怪的,怪僻的;偏执的,异乎寻常的 2. (两个圆)不同圆心的[concentric之对]

·eccentricity n. 1. 古怪,怪僻 2. 偏心

·consequently 因此,结果,所以

·sinusoidal 正弦曲线的

·trajectory 轨迹、轨线、弹道

·excessively 过分的,极度

·guaranteed adj. 有保证的,;有人担保的 v. 担保(guarantee的过去式和过去分词)

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