Sorin G. Stan

Digital servo IC for optical disc drives

Abstract This paper addresses the use of PID regulators to achieve some of the main control goals in an optical disc drive: (i) focusing of the laser spot on the disc surface, (ii) tracking the continuous data spiral during playback, and (iii) radially searching the target location on disc during an access procedure. The paper discusses the servo loops and a dedicated PID-based digital servo integrated circuit (DSIC) employed to perform the control tasks mentioned above.

DVD+RW: 2-way compatibility for video and data applications

This paper discusses the 4.7-GB digital versatile disc plus rewritable (DVD+RW) system as a future replacement for the video cassette recorder (VCR). It is shown that the digital versatile discs can be recorded in a fully compatible manner with the existing DVD-video standard and players. The compatibility issue is addressed from the perspective of the DVD-video physical and logical formats.

Look-ahead seek correction in high-performance CD-ROM drives

As the performance of CD-ROM drives continues to increase, special attention should be paid to any element in the system that disturbs the desired specifications. When very low access times are considered, it is mandatory to reach the target track within only one seek action, i.e. without any consequent retry or correction seek. Many CD-ROM drives count the tracks crossed during seeking and, by comparing this count with the pre-calculated seek length, the exact target location can be detected. This paper considers the error that affects the track-counting mechanism due to the rotating disc spiral. It is shown that, for a given seek length, the number of crossed tracks differs between outside- and inside-oriented seeks. The involved equations are derived and an algorithm proposed for determining the correct number of tracks to be crossed during a seek action. The proposed algorithm, which is optimized for microprocessor implementation, relies on two look-up tables and a learning scheme that allows look-ahead seek correction for both spiral rotation and system tolerances.

Twin-actuators for ultra-fast access in CD-ROM systems

This paper describes the principle of the twin-actuator CD-ROM drive and the improvement it brings to the access performance. After a brief introduction, a novel one-sledge twin-actuator construction is presented which leads to very short seek times. An adaptive twin-actuator construction is also described. Finally, some calculations for systems with two independent actuators are carried out. The seek performance of a twin-actuator drive is calculated as related to a standard CD-ROM benchmark.

DVD+R - a write-once optical recording system for video and data applications

This paper discusses the Digital Versatile Disc plus Recordable (DVD+R) system, which can create non-erasable DVD discs perfectly compatible with the installed based of players and computer drives. The physical and logical formats of DVD+R media are very similar to those of the Digital Versatile Disc plus ReWritable (DVD+RW). It is for this reason that the users of DVD+RW data drives and video recorders can easily upgrade their equipment by software means. The DVD+R systems operate with an increased accuracy of linking data in multisession mode, which makes them suitable for appending video files when building large archives.

A System Analysis for High- and Very High-Speed CD-ROM Drives

Abstract This paper presents an overview of the specific design issues related to the high- and very high-speed CD-ROM drives. The general architecture and key specifications of a CD-ROM system are briefly introduced and various aspects regarding the improvement of these specifications are considered. The strategies employed to control the turntable motor as well as to position the optical head(s) are discussed. The described control techniques and algorithms are specifically aimed to boost the performance of the CD-ROM drives, namely to increase their data throughput and decrease their access time.

High-performance adaptive-speed/CAV CD-ROM drive

This paper describes a novel type of CD-ROM drive which can automatically distinguish between two basic operating modes: continuous playback and continuous access. The drive, based on the adaptive-speed technology, is optimized for a very high data throughput during sustained read-out using a new cubic overspeed profile. In addition, by detecting the state of continuous access and switching the spindle motor into a CAV (constant angular velocity) loop, the drive features very low power consumption. Two dedicated firmware algorithms which can detect one of the two operating modes either at the bit-engine level or at the data-path level are also presented. While implementing the algorithm at the data-path level, the paper also includes a novel technique for the optimization of the data flow via controlling the speed of the spindle motor. A better buffer management can therefore be achieved. Last but not least, the cubic overspeed profile is shown to be optimal not only for sustained playback but also while the drive is performing either a unique seek action or a short sequence of seeks.

Digital Servo IC for Optical Disc Drives

Abstract This paper addresses the use of PID regulators to achieve some of the main control goals in an optical disc drive: (i) focusing of the laser spot on the disc surface, (ii) tracking the continuous data spiral during playback, and (iii) radially searching the target location on disc during an access procedure. The servo loops employed to perform the control tasks mentioned above will be described and a dedicated PID-based digital servo integrated circuit (DSIC) will also be introduced.

Adaptive-speed/CAV algorithm in a CD-ROM drive to accomplish high data transfer rate and low power consumption

This paper presents an adaptive-speed/CAV algorithm which regulates the disc velocity in a CD-ROM system to accomplish high data throughput (bit rate) during continuous playback and low power consumption during continuous data access. The adaptive-speed profile is based upon quasi-CLV control which allows drive optimisation towards both data throughput and access time. The presented algorithm can automatically distinguish between two operating modes-continuous access and continuous playback. By detecting the state of continuous access, the CD-ROM drive switches its spindle-motor loop into a constant angular velocity (CAV) mode, avoiding therefore the acceleration/braking of the motor, and thus reducing the power consumption. By detecting the state of continuous playback, the spindle motor will be set to follow an adaptive-speed profile which is highly optimized for data transfer rate. The software and hardware implementation of the CAV/quasi-CLV switching technique in a CD-ROM system is also described.

From CD to DVD and Beyond

Summary form only given. Recording the information is a habit that goes back in time about 100,000 years, when humans produced apparently their first ornaments. Many global changes have taken places since then and have affected the way we handle the analog and later the digital information. The CD and DVD represent exponents of wonderful technologies we experience daily, but where is optical storage heading to? Will the DVD be replaced? Will holographic storage prevail? We might have some of the answers, but questions like these keep inevitably recurring.