OPTICAL READING METHOD AND OPTICAL READING SYSTEM
An optical reading method which suppresses variations in the reading quality of a low-reflection optical recording medium. The optical reading method is to read information from an optical recording medium by irradiating the medium with read laser light having a wavelength λ of 400 to 410 nm. In this method, an information recording layer of the optical recording medium is irradiated with the read laser light with an average read power P ra in excess of 1.2 mW if the information recording layer has a reflectance of 4% or less.
1 . An optical reading method for reading information from an optical recording medium by irradiating the optical recording medium with read laser light having a wavelength λ of 400 to 410 nm, wherein an information recording layer of the optical recording medium is irradiated with the read laser light with an average read power P ra in excess of 1.2 mW if the information recording layer has a reflectance of 4% or less.
2 . The optical reading method according to claim 1 , wherein the read laser light is used to read the optical recording medium at a reading linear velocity in excess of 4.1 m/s.
3 . The optical reading method according to claim 1 , wherein P rp /P ra <4, where P rp is a peak read power of the read laser light.
4 . The optical reading method according to claim 2 , wherein P rp /P ra <4, where P rp is a peak read power of the read laser light.
5 . The optical reading method according to claim 3 , wherein the read laser light for the information recording layer to be irradiated with is constant light.
6 . The optical reading method according to claim 1 , wherein the read laser light is used to read the optical recording medium at a reading linear velocity in excess of 8.2 m/s.
7 . The optical reading method according to claim 2 , wherein the read laser light is used to read the optical recording medium at a reading linear velocity in excess of 8.2 m/s.
8 . The optical reading method according to claim 3 , wherein the read laser light is used to read the optical recording medium at a reading linear velocity in excess of 8.2 m/s.
9 . The optical reading method according to claim 5 , wherein the read laser light is used to read the optical recording medium at a reading linear velocity in excess of 8.2 m/s.
10 . The optical reading method according to claim 1 , wherein the optical recording medium has two or more information recording layers.
11 . The optical reading method according to claim 2 , wherein the optical recording medium has two or more information recording layers.
12 . The optical reading method according to claim 3 , wherein the optical recording medium has two or more information recording layers.
13 . The optical reading method according to claim 5 , wherein the optical recording medium has two or more information recording layers.
14 . The optical reading method according to claim 6 , wherein the optical recording medium has two or more information recording layers.
15 . The optical reading method according to claim 10 , wherein the optical recording medium has four or more information recording layers.
16 . The optical reading method according to claim 10 , wherein the information recording layers include at least one having a first reflectance and one having a second reflectance different from the first reflectance.
17 . The optical reading method according to claim 15 , wherein the information recording layers include at least one having a first reflectance and one having a second reflectance different from the first reflectance.
18 . An optical reading system comprising:
a rotation drive unit for rotating an optical recording medium including an information recording layer having a reflectance of 4% or less;
a laser light source for generating read laser light having a wavelength λ of 400 to 410 nm;
an objective lens for collecting the read laser light to irradiate the optical recording medium with the read laser light;
a photoelectric transducer for receiving reflected light of the read laser light and converting it into an electronic signal; and
a laser control unit for controlling an average read power P ra of the read laser light to above 1.2 mW.