We present an optical design for Blu-ray pickup head that can synchronously detect a linear displacement and two-dimensional (2D) angular tilt of the test plane. In order to enhance the accuracy of tilt angle and discriminate more tilted orientations, a high resolution detector (177×177 pixels) is used as the photo detector of the Blu-ray pickup head. The horizontal beam expander is used to make the laser beam be more uniform to improve the accuracy of signal at the photo detector. The signal at the high resolution detector of the pickup head used astigmatic detection is comprised of two displacement signals and one angular signal. The displacement of the test plane is ascertained from the rate of change in the length of semi-major and semi-minor axis for elliptical beam shape on the high resolution detector. The tilt of the test plane is obtained from the brightest position of beam shape. It is not only able to judge the tilt angle for four orientations (α, β, 45°and 135°), but also the tilt angle for four orientations (30°, 60°, 120°and 150°). The smaller pixel size will help to improve the accuracy in the 2D angle measurement further.
|Number of pages||5|
|State||Published - 2011|
|Event||International Conference on Optics in Precision Engineering and Nanotechnology, ICOPEN 2011 - Singapore, Singapore|
Duration: 23 Mar 2011 → 25 Mar 2011
- Blu-ray pickup head
- High resolution detector
- Laser expander