Patent ID: 8363532
Filing Date: 2013-01-29
Classification: G11B

Abstract:
1. A method of controlling a position in which data is to be recorded on a holographic data recording medium by using interference between a reference light and a signal light, the method comprising: transmitting a servo light through a reflective transmission layer of the holographic data recording medium; irradiating the reference light and the signal light on the holographic data recording medium; generating a focus error signal that indicates a distance difference between a first focus corresponding to a focus of the reference light on the holographic data recording medium and a second focus corresponding to a focus of the signal light on the holographic data recording medium, based on information about a reflective signal light generated when the irradiated signal light is reflected from the reflective transmission layer; moving the second focus to a position of the first focus, based on the generated focus error signal; determining whether the distance difference between the first focus and the moved second focus is less than a threshold value; and in response to the determined distance difference between the first focus and the moved second focus being less than the threshold value, driving a servo controller that automatically controls servos in response to the generated focus error signal so that the second focus coincides with the first focus.