Reliability by robust design for optical alignment in a CD pickup

Micron-level alignment of optical components in the laser pickup of a compact disc (CD) system is critical for its performance. The robustness of the rotational alignment of the laser/diffraction grating unit (LDGU) is studied in detail in this paper using finite element analysis and Robust Design tools. Robust design simulations were constructed in terms of the process capability indices C-p, C-pk, and yield of the clamper arms used to hold the LDGU in place. Effects of force and torsional load from the actual process were taken into consideration during the simulations, Experimental measurement was used to verify the finite element analysis. The results from both experimental and theoretical analyzes were applied to concurrently modify the design of the clamper arms, reducing the fall-off rate (FOR) in the production of the laser pickup by 10%. It is demonstrated that the finite element analysis together with the Robust Design approach form a very powerful tool for the designer to achieve the required reliability targets for the product.