Patent ID: 6501712
Filing Date: 2002-12-31
Classification: G11B

Abstract:
A method for identifying discs in an optical disc device, wherein the optical disc device contains a first light source operable to radiate a light beam with a first wavelength for reproducing information from a first optical disc, a second light source operable to radiate a light beam with a second wavelength which is shorter than the first wavelength for reproducing information from a second optical disc having a higher recording density than the recording density of the first optical disc, a convergent device operable to have the light beams of the first and second wavelengths converge on the optical disc, and a light receiving device operable to receive reflected light from the first and second optical discs, said method comprising:irradiating the light beam of the first wavelength on an optical disc while rotation of the optical disc is suspended; recognizing the existence of the first optical disc according to a signal received from the light receiving device when a focal point of the convergent device is moved in a light irradiating axis direction to the optical disc; switching off the first light source and irradiating the light beam of the second wavelength on the optical disc while the rotation of the optical disc is still suspended when no existence of the first optical disc is recognized; recognizing the existence of the second optical disc according to a signal received from the light receiving device when a focal point of the convergent device is moved in the light irradiating axis direction to the optical disc; memorizing a signal received from the light receiving device when no existence of the first optical disc is recognized by irradiating the light beam of the first wavelength; irradiating the light beam of the second wavelength in succession to memorize a signal received from the light receiving device to recognize the existence of the second disc; and judging the existence of the first optical disc again by making a comparison between the values of two memorized signals.