KEYWORDS: Servomechanisms, Control systems, Actuators, Infinite impulse response filters, Human-machine interfaces, Channel projecting optics, Device simulation, Digital signal processing, Digital video discs, Computer simulations
CBHD (China Blue High Definition Disc) is a high-definition optical disc standard with Chinese independent intellectual
property. Compared with DVD optical pick-up, CBHD optical pick-up, key component of CBHD player, has significant
improvement in the channel bit rate and certain reduction in acceptable tolerance range for disk tilt, etc. This paper
specifies the servo control system construction for the CBHD radial tracing and axial tracking. This servo control system
should ensure the optical beam of OPU focusing on the Disc plane and following the track of CBHD channel accurately.
According to the expected radial/axial maximum acceleration and the limitation of emax, an open-loop transfer function
specifying the servo system for axial and radial tracking is introduced. The corresponding servo control algorithm
including IIR filter based on the above-mentioned transfer function is theoretically analyzed and numerically simulated
by MATLAB. Because optical pick-ups are different in dynamic properties and its digital circuit exist quantization error,
time delay nonlinearity, etc, the tuning of IIR parameters is laborious and time-consuming. Thus a experimental platform
for CBHD optical pick-up servo system are designed in this paper, and an user-friendly interface for IIR parameters
adjustment is given. Experimental results showed that this control system has good servo characteristics in time-domain
and frequency-domain.
The optical pickup unit is a kind of mass-produced product as well as a diffraction-limited micro-optical system.
Thus the optical elements are assembled serially in the production line, and its fabricating and assembling errors should
be controlled to achieve a diffraction-limited focus spot on the disk. And the reflected light from the disk on the photo
detector would be converted and processed in the servo control system and evaluated using the electrical evaluator. Thus
a correlation between the electrical evaluator and the spot intensity should be considered when setting the testing
standard for a production line.
In this paper, the optical pickup is measured using a spot analyzing system. Its electrical signals are described in the
evaluator. The optical system in the optical pickup would be divided into two testing parts: base part and focusing part.
The base part includes the laser diode, collimator, prism, quarter-wave-plate, beam splitter and reflective mirror; while
the focusing part has objective lens, phase plate, wave-plate, and so on. The focus quality is measured using the spot
analyzer. Then these optical pickups are processed to get the electrical signals directly from the evaluator. Finally the
parameters achieved using these two systems are compared and its correlation are investigated. This method is verified
when designing a DVD production line and might be useful in establishing the standards for a new optical pickup.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.