Information recording apparatus having automatic focusing

Claim 2

An information recording apparatus comprising: a light source of emitting a first light beam; first means for applying predetermined recording information to said first light beam emitted from said light source to produce a pulsated light beam; second means for irradiating said pulsated light beam onto a predetermined recording medium, said recording medium having a reflectivity thereto to said pulsated light beam which lowers below a predetermined value during the period of irradiation of said pulsated light beam as a result of the formation of a pit in said recording medium; third means for detecting a second light beam which is a reflected version of said pulsated light beam from said recording medium before the reflectivity of said recording medium lowers below said predetermined value; fourth means for producing an automatic focusing signal in accordance with an output from said third means, said automatic focusing signal having a predetermined frequency relation to the frequency of the predetermined recording information so as to enable sampling of said automatic focusing signal by the frequency of the predetermined recording information, the predetermined frequency relation being that the frequency of said automatic focusing signal is equal to or lower than one-half of the frequency of the predetermined recording information; and fifth means responsive to an output from said fourth means for focusing said pulsated light beam onto said recording medium.

Claim 3

An information recording apparatus according to claim 1, wherein said fourth means includes a low pass filter for receiving the output from said third means.

Claim 4

An information recording apparatus according to claim 1, wherein said fourth means includes a differential amplifier.

Claim 5

An information recording apparatus according to claim 3, wherein said fourth means further includes a low pass filter connected to receive an output of said differential amplifier.

Claim 6

An information recording apparatus according to claim 1, wherein said third means detects the second light beam produced prior to the reflectivity of said recording medium being lowered below a predetermined value for enabling production of said automatic focusing signal by said fourth means.

Claim 7

An information recording apparatus comprising: a gas laser for emitting a first light beam; an information source for generating a recording information signal; a light modulator for modulating said first light beam emitted from said gas laser in accordance with said recording information signal to produce a pulsated light beam; a first optical system for irradiating said pulsated light beam onto a predetermined recording medium, said recording medium having a reflectivity thereof to said pulsated light beam which lowers below a predetermined value during the period of irradiation of said pulsated light beam as a result of the formation of a pit in said recording medium; a light detector having a quartered light receiving surface for detecting a second light beam which is a reflected version of said pulsated light beam from said recording medium before the reflectivity of said recording medium lowers below said predetermined value; a cylindrical lens positioned between said recording medium and said light detector for directing said second light beam to said light detector: automatic focusing signal generating means for receiving an output from said light detector to produce an output of an automatic focusing signal, said automatic focusing signal having a predetermined frequency relation to the frequency of said recording information signal so as to enable sampling of said automatic focusing signal by the frequency of said recording information signal, the predetermined frequency relation being that the frequency of said automatic focusing signal is equal to or lower than one-half of the frequency of said recording information signal; and a second optical system responsive to the output of said automatic focusing signal generating means for focusing said pulsated light beam onto said recording medium.

Claim 8

An information recording apparatus comprising: a gas laser for emitting a first light beam; an information source for generating a recording information signal; a light modulator for modulating said first light beam emitted from said gas laser in accordance with said recording information signal to produce a pulsated light beam; a first optical system for irradiating said pulsated light beam onto a predetermined recording medium, said recording medium having a reflectivity thereof to said pulsated light beam which lowers below a predetermined value during the period of irradiation of said pulsated light beam as a result of the formation of a pit in said recording medium; a light detector having a quartered light receiving surface for detecting a second light beam which is a reflected version of said pulsated light beam from said recording medium before the reflectivity of said recording medium lowers below said predetermined value; a cylindrical lens positioned between said recording medium and said light detector for directing said second light beam to said light detector: automatic focusing signal generating means for receiving an output from said light detector to produce an output of an automatic focusing signal, said automatic focusing signal having a predetermined frequency relation to the frequency of said recording information signal so as to enable sampling of said automatic focusing signal by the frequency of said recording information signal, the predetermined frequency relation being that the frequency of said automatic focusing signal is equal to or lower than one-half of the frequency of said recording information signal; and a second optical system responsive to the output of said automatic focusing signal generating means for focusing said pulsated light beam onto said recording medium.

Claim 9

An information recording apparatus comprising: an information source for generating a recording information signal; a semiconductor laser element modulated in accordance with said recording information signal for emitting a first pulsated light beam; a first optical system for irradiating said first pulsated light beam onto a predetermined recording medium, said recording medium having a reflectivity thereof to said first pulsated light beam which lowers below a predetermined value during the period of irradiation of said first pulsated light beam as a result of the formation of a pit in said recording medium; a light detector having a quartered light receiving surface for detecting a second pulsated light beam which is a reflected version of said first pulsated light beam of said recording medium before the reflectivity of said recording medium lowers below said predetermined value; a cylindrical lens positioned between said recording medium and said light detector for directing said second pulsated light beam to said light detector; automatic focusing signal generating means for receiving an output from said light detector to produce an output of an automatic focusing signal, said automatic focusing signal having a predetermined frequency relation to the frequency of said recording information signal so as to enable sampling of said automatic focusing signal by the frequency of said recording information signal, the predetermined frequency relation being that the frequency of said automatic focusing signal is equal to or lower than one-half of the frequency of said recording information signal; and a second optical system responsive to the output of said automatic focusing signal generating means for focusing said first pulsated light beam onto said recording medium.

Claim 10

An information recording apparatus comprising: an information source for generating a recording information signal; a semiconductor laser element modulated in accordance with said recording information signal for emitting a first pulsated light beam; a first optical system for irradiating said first pulsated light beam onto a predetermined recording medium, said recording medium having a reflectivity thereof to said first pulsated light beam which lowers below a predetermined value during the period of irradiation of said first pulsated light beam as a result of the formation of a pit in said recording medium; a light detector having a quartered light receiving surface for detecting a second pulsated light beam which is a reflected version of said first pulsated light beam of said recording medium before the reflectivity of said recording medium lowers below said predetermined value; a cylindrical lens positioned between said recording medium and said light detector for directing said second pulsated light beam to said light detector; automatic focusing signal generating means for receiving an output from said light detector to produce an output of an automatic focusing signal, said automatic focusing signal having a predetermined frequency relation to the frequency of said recording information signal so as to enable sampling of said automatic focusing signal by the frequency of said recording information signal, the predetermined frequency relation being that the frequency of said automatic focusing signal is equal to or lower than one-half of the frequency of said recording information signal; and a second optical system responsive to the output of said automatic focusing signal generating means for focusing said first pulsated light beam onto said recording medium.

Claim 11

An information recording apparatus according to claim 1, 6 or 7, wherein said recording medium is made of metal material.

Claim 12

An information recording apparatus according to claim 1, 6 or 7, wherein said recording medium is made of Calcogenide glass material.

Claim 13

An information recording apparatus according to claim 6 or 7, wherein said automatic focusing signal generating means includes a low pass filter.

Claim 14

An information recording apparatus according to claim 6 or 7, wherein said automatic focusing signal generating means includes a differential amplifier.

Claim 15

An information recording apparatus according to claim 11, wherein said automatic focusing signal generating means further includes a low pass filter connected to receive an output of said differential amplifier.

Claim 16

An information recording apparatus comprising: light beam emitting means for emitting a pulsated light beam having an intensity thereof modulated in accordance with information to be recorded; a recording medium irradiated with said pulsated light beam, said recording medium having a reflectivity thereof to said pulsated light beam which does not change during a predetermined period within the time of irradiation of said pulsated light beam and thereafter lowers as a result of the formation of an information pit in said recording medium; a first optical system including a focusing lens for focusing said pulsated light beam onto said recording medium; light detecting means for converting a reflected version of said pulsated light beam from said recording medium into an electric signal; a second optical system for deriving reflected light which is a reflected version of said pulsated light beam from said recording medium and for introducing said reflected light to said light detecting means; focus error signal detecting means for detecting a focus error signal in accordance with the portion of the output of said light detecting means which is present in said predetermined period in which the reflectivity of said recording medium does not change; and means responsive to the output of said focus error signal detecting means for adjusting a distance of said focusing lens from said recording medium so that said pulsated light beam is correctly focused onto said recording medium during the recording of information thereon.

Claim 17

An information recording apparatus comprising: light beam emitting means for emitting a pulsated light beam having an intensity thereof modulated in accordance with information to be recorded; a recording medium irradiated with said pulsated light beam, said recording medium having a reflectivity thereof to said pulsated light beam which does not change during a predetermined period within the time of irradiation of said pulsated light beam and thereafter lowers as a result of the formation of an information pit in said recording medium; a first optical system including a focusing lens for focusing said pulsated light beam onto said recording medium; light detecting means for converting a reflected version of said pulsated light beam from said recording medium into an electric signal; a second optical system for deriving reflected light which is a reflected version of said pulsated light beam from said recording medium and for introducing said reflected light to said light detecting means; focus error signal detecting means for detecting a focus error signal in accordance with the portion of the output of said light detecting means which is present in said predetermined period in which the reflectivity of said recording medium does not change; and means responsive to the output of said focus error signal detecting means for adjusting a distance of said focusing lens from said recording medium so that said pulsated light beam is correctly focused onto said recording medium during the recording of information thereon.

Claim 18

An information recording apparatus according to claim 13, wherein said focus error signal detecting means includes a low pass filter.

Claim 19

An information recording apparatus according to claim 14, wherein said light beam emitting means includes a semiconductor laser and an information source for generating an information signal which modulates said semiconductor laser.

Claim 20

An information recording apparatus according to claim 14, wherein said light beam emitting means includes a gas laser, a light modulator for modulating a light beam from said gas laser, and an information source for generating an information signal which drives said light modulator.

Claim 21

An information recording apparatus according to claim 13, wherein said light beam emitting means includes a semiconductor laser and an information source for generating an information signal which modulates said semiconductor laser.

Claim 22

An information recording apparatus according to claim 13, wherein said light beam emitting means includes a gas laser, a light modulator for modulating a light beam from said gas laser, and an information source for generating an information signal which drives said light modulator.