Method for determining recording exposure for holographic recording medium and method for recording thereon

A method for determining a recording exposure to record a plurality of elemental holograms when forming the elemental holograms on a holographic recording medium to create a three-dimensional image, the method comprising:

• a bright pattern image recording step including a first bright pattern image recording substep of continuously recording a plurality of elemental holograms with a first stage recording exposure to record a first bright pattern image which is brighter at a central portion than at a peripheral portion, and second to nth bright pattern image recording substeps of recording second to nth bright pattern images having the same pattern as that of the first bright pattern image with a recording exposure varied in second to nth stages;
• a dark pattern image recording step including a first dark pattern image recording substep of continuously recording a plurality of elemental holograms with the same recording exposure as that for the first stage in the first bright pattern image recording substep to record a first dark pattern image, the first dark pattern image having a central portion darker than a peripheral portion and having reversed bright and dark portions with respect to the first bright pattern image, and second to nth dark pattern image recording substeps of recording second to nth dark pattern images with the same recording exposure as that for the second to nth stages, the second to nth dark pattern images having the same pattern as that of the first dark pattern image;
• a step of irradiating the first to nth bright pattern images and the first to nth dark pattern images with a read beam to detect an intensity of a diffracted beam occurring from each image;
• an SNR calculating step of calculating Sa1/Sb1=SNR1, Sa2/Sb2=SNR2, . . . , and San/Sbn=SNRn, where Sa1 to San are an intensity of a diffracted beam from the first to nth bright pattern images and Sb1 to Sbn are an intensity of a diffracted beam from the first to nth dark pattern images;
• an SNRmax determining step of determining an SNRmax being the maximum of the resulting SNR1, SNR2, . . . , and SNRn;
• and
• a step of determining a recording exposure at the SNRmax as an optimal recording exposure among the recording exposures in the first to nth stages.