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A novel design of HD–DVD optical pick-up head is proposed. The geometrical size of the pick-up head is reduced by using a combined system of a Penta prism and an aspherical lens. Such a combined system can replace the mirror and collimating lens in a conventional pick-up head, to achieve a miniature HD–DVD pick-up head.

An improved optimization method is presented for doublet design using the shape factor of the third-order aberrations of a thick lens to compensate high-order aberrations. This method can effectively evaluate a minimal area of aberration curves bounded by the ray-fan diagram. For the proposed optimization program, taking the RMS value of the spot diagram to be less than the diffraction limited value of the point spread function (PSF) as the evaluated criterion is suggested. The design specifications for the optimized doublet are F/3.333 and semi-field angle of 1°, within the visible spectral range. Two design examples of the doublet, one a glass lens and the other a plastic lens, are presented. The results show well-designed doublets when compared with Kingslake's design.