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.