A refractive astigmatic lens is employed to generate a focus error signal (FES) for servo control in general optical pickup. In
this paper, a diffractive optical element (DOE) is designed to implement optical functions of astigmatic focusing for a
MEMS-based miniature optical pickup at 650nm wavelength. We present a diffractive astigmatic lens with its internal zones
and external zones quantized into four, two phase levels, respectively based on fabrication consideration. The optical
simulation based on scalar diffraction theory shows the efficiency of this quantized lens for astigmatic focusing and a
comparison of the FES in the optical pickup system has been plotted.
The majority of the beam splitters for three beam tracking in commercial DVD pickup employ lamellar phase gratings, which already provides sufficient efficiency. However, for a pickup with all diffractive elements, the power budget becomes more critical, and a higher efficiency of the beam splitter is required. In this paper, we have investigated and will present the influence of the desired energy ratio between the zeroth order central beam to the first order side beam on the total efficiency of the beam splitter. The simulation based on scalar diffraction theory shows that the total efficiency of a lamellar phase grating will drop as the ratio decrease, which can be improved by employing a more sophisticated surface relief. The equal-side triangular profile has been investigated as a solution and the geometrical size of the profile has been optimized for several desired energy ratio. For a low cost fabrication process with photolithography, the total efficiency loss due to quantization with different quantization levels of the triangular surface relief has been estimated with scalar diffraction theory. This paper is concluded with a table of optimal phase level for a given energy ratio and desired minimum total efficiency with the consideration of fabrication cost.