Optical information recording medium and information recording and reproducing method thereof

An optical information recording medium comprising a substrate and a recording layer formed thereon;

• said substrate comprising a guide groove with a concave portion and a convex portion;
• and at least two sample pits shifted on both sides from a central line of the guide groove on a region where the guide groove is interrupted;
• said recording layer undergoing optically detectable changes by an application of a light beam;
• the optically detectable changes of the layer being caused by a change in an optical phase of a reflection light or a transmission light from the recording layer;
• the change in the optical phase is in a direction of reducing an optical phase difference between the concave portion and the convex portion of the guide groove.

An optical information recording medium comprising a substrate and a recording layer formed thereon;

• said substrate comprising a pit capsule string composed of a circular concave portion or a convex portion provided at a constant interval on a track;
• and at least two sample pits provided in a position shifted from a central line of the pit capsule string where the pit capsule string is interrupted;
• said recording layer undergoing optically detectable changes by an application of a light beam;
• the optically detectable changes of the layer being caused by a change in the optical phase of a reflection light or a transmission light from the recording layer;
• and the change in the optical phase is in a direction of reducing an optical phase difference between the concave portion and the convex portion of the pit capsule string.

An information recording and/or reproducing method using an optical information recording medium comprising a substrate and a recording layer formed thereon,

• said substrate comprising a guide groove with a concave portion and a convex portion;
• and at least two sample pits shifted on both sides from a central line of the guide groove on a region where the guide groove is interrupted;
• said recording layer undergoing optically detectable changes by an application of a light beam;
• the optically detectable changes of the layer being caused by a change in an optical phase of a reflection light or a transmission light from the recording layer;
• the change in the optical phase is in a direction of reducing an optical phase different between the concave portion and the convex portion of the guide groove
• irradiating a light beam onto a guide groove formed on a recording medium or onto a pair of sample pits provided in a region where capsule pits are interupted;
• detecting reflected light or transmitted light from the recording medium;
• and
• effecting a tracking control by reducing a difference in an amount of light between the reflected light and the transmitted light between a pair of the sample pits.

An apparatus for recording and/or reproducing information on and/or from a recording medium, said recording medium comprising:

• a recording layer disposed on a substrate, said layer undergoing optically detectable changes by an application of a light beam;
• said substrate being provided with a guide groove having concave and convex portions;
• a width of said grove being smaller than a spot diameter of the light beam focused on the recording layer;
• said recording layer undergoing a change of optically detectable states by application of the light beam modulated in accordance with an information signal;
• the change of the optically detectable states of the recording layer with absorption of the light beam being from a first state into a second state upon receipt of the application of the light beams at a first intensity of the light while the optically detectable states of the recording layer being changed into the first state from the second state upon receipt of the application of the light beam at a second intensity lower than the first intensity;
• the regions of the first and second states of the recording layer having complex refractive indexes which are different from each other, the difference of the complex refractive indexes causing a change in an optical phase of light reflected from the recording layer having the light beam applied thereto;
• the change of the optical phase from the first state to the second state being in a direction towards reducing an optical phase difference between the concave portion and the convex portion of said guide groove;
• said light beam being composed of at least three spot strings;
• a line passing through the centers of the spots of the three light strings being oblique with respect to the guide groove on the recording layer;
• the information signal of said recording layer being reproduced by detecting the reflected light or transmitted light from a first spot positioned at the center of a first spot string;
• the first spot being tracked on the guide groove to effect a tracking control by detecting the transmitted light or reflection light from the second and third spots positioned before and after the first spot.