Patent ID: 7518972

Claim:
A holographic multiplex recording method for forming recording spots, which are an overlapping projection region of an object beam and a reference beam, so as to be superimposed with a slight shift relative to one another in an X-axis direction and a Y-axis direction when interference fringes are formed in a recording layer in a holographic recording medium by projecting the object beam and the reference beam, the holographic multiplex recording method comprising: an X-axis direction first multiplex recording step of forming a first-stage multiplex recording spot matrix, comprising, a step of forming a first recording spot matrix by forming and arranging recording spot rows comprising recording spots arranged with a constant pitch in the X-axis direction without overlapping, with a constant pitch in the Y-axis direction without overlapping, a step of forming a second recording spot matrix by forming and arranging recording spot rows comprising recording spots slightly phase-shifted in the X-axis direction with respect to the first recording spot matrix and having the same phase and the same pitch in the Y-axis direction as those of the first recording spot matrix, with a constant pitch in the Y-axis direction without overlapping, and a step of forming a third recording spot matrix to a last recording spot matrix by repeating formation of recording spot rows comprising recording spots slightly phase-shifted in the X-axis direction with respect to the recording spot rows of the previous recording spot matrix and having the same phase and the same pitch in the Y-axis direction as those of the recording spot rows of the previous recording spot matrix, with a constant pitch in the Y-axis direction without overlapping until immediately before the total sum of the phase shift in the X-axis direction from the first recording spot matrix to a last recording spot matrix becomes the same as the pitch between the recording spot rows in the X-axis direction; and a step of forming a second-stage to a last-stage multiplex recording spot matrices by an X-axis direction second multiplex recording step to an X-axis direction last multiplex recording step which are similar to the X-axis direction first multiplex recording step and repeat thereof, wherein: the total sum of the phase shift from the first recording spot matrix to the last recording spot matrix in the X-axis direction is set until immediately before the total sum becomes the same as the pitch between the recording spot rows in the X-axis direction; and the X-axis direction second multiplex recording step to the X-axis direction last multiplex recording step are performed by slightly shifting the phase relative to one another in the Y-axis direction with respect to each of the recording spot rows in the X-axis direction first multiplex recording step until immediately before the total sum of the phase shift in the Y-axis direction up to the X-axis direction last multiplex recording step becomes the same as the pitch between the recording spot rows in the Y-axis direction.