Recording of multiplexed microholographic gratings with improved recording volume for high density optical data storage is proposed and demonstrated. By using a hybrid diffractive–refractive objective lens with extended depth of focus, we have achieved a recording beam size of approximately $1\mathrm{\mu }\mathrm{m}$ and a focal depth of $20\mathrm{\mu }\mathrm{m}$ . Multiple gratings corresponding to spectral lines within the $400–650\mathrm{nm}$ spectral band have been successfully multiplexed in a single recording spot or pit of size $1.25\mathrm{\mu }\mathrm{m}$ on a DuPont photopolymer film using a white light source along with narrowband filters or dispersion elements, thus demonstrating the storage of multiple bits in a single pit. Simultaneous readout of multiple bits in a single storage pit is accomplished with a microspectrometer-type readout head using a white light source.