Basic knowledge of Optical drive

I. Basic knowledge of optical drive

Before you choose a good CD-ROM drive, understand some of the concepts about the optical drive. First I say what is CLV and CA V disc and hard disk work in a very different way, the disc of the hard disk is divided into concentric circles, these concentric circles become the track, each track is divided into a number of sectors, the file is stored in these sectors, therefore, the disk of the hard drive is always rotating at a constant angular speed, which is CA V However, because the disc has a certain radius, this will cause the sector in the disc inside and outside the density of different degrees, the reading data caused a lot of.

The CD-ROM uses a continuous rotating orbit to store data in a somewhat similar sense to the track, which is divided into areas of the same size and density, so that the utilization of the platters is further improved. Since the data on the CD is stored at the same density, it is necessary to take a constant line speed when reading the disc, which is the direct effect of the speed of the CLV constant line is that the optical drive will rotate at a very different speed when reading the inner and outer loop data. This requires the spindle motor of the optical drive to change the rotation speed to accommodate the need to read the data. Readers can imagine that frequent conversion of speed will inevitably lead to a reduction in motor life. But because of the early optical drive, spindle motor speed is not very fast, so there is no big relationship, with the speed of the CD-ROM drive constantly improve the speed of the transformation of the motor to the impact of the optical drive life is increasingly serious, so the current high-speed optical drive are using the CA V technology, that is, the disc a constant line speed rotation Although this extended the optical drive life, but in the reading of the inner circle data, the actual transmission speed will be affected, therefore, some high-end optical drive and the use of CA V and CL

V binding method. In this way, the CA V method is used when reading the inner loop data, and the CLV is used when the outer ring is read, so the performance of the optical drive is further improved. When choosing an optical drive, you should try to choose the optical drive using CA V/CLV technology.

The transmission speed of optical drive is an important factor affecting its performance. Single-speed optical drive transmission rate is 150KB/40 speed of the optical drive is X 150kb/so, the faster the optical drive, the faster the transmission speed. The transfer mode of the optical drive also has an effect on the transmission speed. The current main models are PIO and Ultra mda/33 UMDA 332 species. In contrast, the UMD mode CD-ROM has a lower CPU share and can improve the speed of I/O systems and so on. In addition, the optical drive's seek time and buffer also affect the performance of the optical drive. Seek time refers to the length of time that a laser head adjusts the early technical data after receiving a command to read the data. As a result, the CD-ROM drive has a shorter seek time and better. Buffers (buffer) have a greater impact on the performance of optical drives. Buffer large optical drive in the reading file when its speed advantage is obvious, buy the time should choose larger buffer products, but the use of large capacity Buffer optical drive prices generally more expensive. At present, the main optical drive adopts 128KB buffer. The optical drive interface is divided into IDE and SCSI two kinds. SCSI interface of the optical drive performance advantages are obvious, with a smaller CPU occupancy rate, more stable transmission speed and so on. However, the SCSI interface of the optical drive price is more expensive, so the home to choose the optical drive or the IDE interface for the good.

With the Wan drive, the drive spindle motor speed has reached very fast speed. Therefore, when reading the disk, it will produce great vibration and noise. In order to cope with these negative effects, manufacturers can say that at all costs, the development of their own vibration-proof technology. Rubber damping bracket is such a case of the resulting rubber bracket will be the CD-ROM drive tray and the front cover split, reducing vibration. This has a significant effect on reducing the noise of the optical drive. In addition, in order to improve the accuracy of the optical drive laser, the current high-end optical drive has adopted a suspension of the bald structure, so that the bald head of the addressing and focus time to reduce a lot, and greatly improve the CD-ROM drive capacity. ABS Automatic balance system is also a recent development of an advanced technology (note, not on the car ABS technology under the CD-ROM drive tray placed ball to improve the optical drive reading density uneven disk performance, which for China's CD market is very important. At present, a large number of D plate in the domestic market, and the quality of these platters is usually poor, so the ABS technology has played a power. When the optical drive reads uneven disk, the ball under the tray due to the role of centrifugal force, will run to the side of the light quality to adjust the balance. In addition, such as Metal machine heart, intelligent control circuit and other new technologies are also used in some brands of optical drive, can improve the life of the optical drive and read disk capabilities.

　　Two. Operating principle of optical drive

Let me take a look at how the optical drive works. The laser head is the heart of the optical drive and the most delicate part. Mainly responsible for data reading, so be careful when cleaning the inside of the optical drive. The laser head mainly includes: Laser generator (also known as laser diode) semi-reflective prism, objective lens, lenses and photodiode these parts. When the laser head reads the data on the disc, the laser beam emitted from the laser beam is assembled on the objective lens through a half reflection prism, which focuses the laser into a very small point of light and hits the disc. At this point, the reflected material on the disc will reflect the light coming back, through the objective lens, and then to the half reflection prism. At this point, because the prism is a half reflective structure, it does not allow the beam to penetrate it and return to the laser generator, but through reflection, through the lens, up to the photodiode. Because the surface of the disc is a raised uneven point to record the data, so reflected light will be in different directions. People would define signals in different directions as "0 or" 1 LEDs receive those data in "0 1" and eventually parse it into the data I need. This is how the optical drive works.

During the whole process of reading the data, the tracing and focusing directly affect the error-correcting ability and the stability of the optical drive. Tracing is the insistence that the laser head can always correctly align the track of the recorded data. When the laser beam coincides with the orbit, the trace error signal is 0 or the trace signal may be positive or negative, and the laser head will adjust the posture according to the trace signal. If the CD-ROM drive performance is very poor, read the disk will appear reading data error phenomenon, the most typical is the pronunciation of the track when the phenomenon of the jump.

Focusing means that the laser beam can accurately hit the disc and receive the strongest signal. When the laser beam bounces back from the platter, it hits 4 photodiode at the same time. The signal is superimposed and eventually formed a focused signal. Only if the focus is accurate, the signal is 0 otherwise, the signal will be emitted to correct the position of the laser head. Focusing and seeking are two of the most important performances of the laser head, and the CD-ROM is a good performance in both aspects.