With the advent of dvd, dvd and cd to produce interoperable components, optical systems are more complex, and more tiny lenses, the number of optical elements include lenses, including reduced. In order to function complex optical components focused on an optical element, have given rise to the use of diffraction effects of the hologram element.

dvd and cd (including cd-rom) disk position signal varies, therefore, to read out the signal of the focus position of the laser focus is different, brought together through the lens of two different focal positions. Lens having such a function is called bifocal hologram lens, wherein, in the non-spherical lens of a focal position of the focus, the light diffracted by the aspherical lens on the diffraction grating generated by engraving, the focusing another focus. This lens mold machining tool must have a high-precision circular cutting edge, so that when using the mold aspherical lens, can maintain a high contour accuracy. Holographic diffraction grating micro machining, tool requirements must have a very sharp cutting edge. Has now been developed to meet such requirements upc-r tool, its nose radius for r5μm. When upc-r tool nose radius is large, in the processing of micron diffraction grating, the diffraction grating showing parts of the arc-shaped grooves, the optical performance will be greatly diminished; when nose radius reduced to 5μm When processing a diffraction grating groove will be very precise, the optical performance has been greatly improved. In addition, the circular cutting edge contour accuracy r5μm reaches 50nm, this high-precision cutting edges through ultra-precision machine tools, machine out of high precision aspheric shape, its optical properties are fully able to meet the standards required level. To further enhance the optical performance of bifocal lenses, you should develop a smaller tip arc (eg r1μm) tool.