Optical pickup, information recording apparatus and information reproducing apparatus

An information recording apparatus comprising

• (A) an optical pickup comprising:
• a light emitting device for emitting a light beam onto a record medium comprising a transparent layer, which is transparent for the in light beam and through which the light beam is transmitted;
• a light receiving device for receiving a reflection light of the light beam from said record medium;
• a liquid crystal compensating device for compensating birefringence, which is generated in the light beam when the light beam is transmitted through the transparent layer, on the basis of the reflection light received by said light receiving device, by controlling an orientation direction of liquid crystal molecules in a liquid crystal layer so as to give a canceling phase difference, which is to cancel the birefringence, to the light beam transmitted through the liquid crystal layer;
• a generating device for generating an indication signal indicative of the birefringence on the basis of the reflection light received by said light receiving device;
• and
• a controlling device for controlling the orientation direction on the basis of the indication signal so that a first angle between a standard line, which is perpendicular to an optical axis of the light beam and is set in advance, and the orientation direction in a plane perpendicular to the optical axis is kept to be constant and that a second angle between the optical axis and the orientation direction in a plane including the optical axis is changed, to thereby generate the canceling phase difference in the light beam transmitted through the liquid crystal compensating device,
• (B) a detecting device for detecting record control information, which is recorded in advance on said record medium, on the basis of the reflection light received by said light receiving device, and
• (C) a modulating device for modulating record signal to be recorded onto said record medium on the basis of the detected record control information, to thereby generate a modulation signal which controls said light emitting device to emit the light beam having an intensity corresponding to the modulation signal.

An information reproducing apparatus comprising

• (A) an optical pickup comprising:
• a light emitting device for emitting a light beam onto a record medium comprising a transparent layer, which is transparent for the light beam and through which the light beam is transmitted;
• a light receiving device for receiving a reflection light of the light beam from said record medium;
• a liquid crystal compensating device for compensating birefringence, which is generated in the light beam when the light beam is transmitted through the transparent layer, on the basis of the reflection light received by said light receiving device, by controlling an orientation direction of liquid crystal molecules in a liquid crystal layer so as to give a canceling phase difference, which is to cancel the birefringence, to the light beam transmitted through the liquid crystal layer;
• a generating device for generating an indication signal indicative of the birefringence on the basis of the reflection light received by said light receiving device;
• and
• a controlling device for controlling the orientation direction on the basis of the indication signal so that a first angle between a standard line, which is perpendicular to an optical axis of the light beam and is set in advance, and the orientation direction in a plane perpendicular to the optical axis is kept to be constant and that a second angle between the optical axis and the orientation direction in a plane including the optical axis is changed, to thereby generate the canceling phase difference in the light beam transmitted through the liquid crystal compensating device, and
• (B) a reproducing device for reproducing record information, which is recorded in advance on said record medium, on the basis of the reflection light received by said light receiving device, to thereby output a reproduction signal to an external portion.