Multiple data surface optical data storage system

An optical data storage system comprising:

• a light source for producing a light beam;
• an optical medium comprising a first light transmissive substrate having a first light transmissive data surface for storing recorded data, the first data surface having marks which are optically detectable;
• a second substrate having a second data surface for storing recorded data, the second data surface having marks which are optically detectable;
• a spacer means located between the first and second substrates for defining a space between the first and second data surfaces, the space containing a gas such that the light beam is selectively focussed through the first light transmissive member to one of the first and second data surfaces, the spacer means having a passage connecting the space with the atmosphere outside the medium, the passage allowing the movement of gas between the space and the atmosphere outside the medium and the passage blocking the movement of solid particles between the space and the atmosphere outside the medium;
• data surfaces of the optical medium;
• and
• an optical data reception means for receiving a reflected light beam from the optical medium and providing a data signal responsive thereto.

An optical data storage system comprising:

• a light source for producing a light beam;
• an optical medium comprising a first light transmissive member consisting of a nonmetallic material and having a noncoated first data surface, the first data surface having marks which are optically detectable, the marks being integral to the first light transmissive member;
• a second member having a second data surface, the second data surface having marks which are optically detectable, the marks being integral to the second member;
• a spacer means located between the first and second members for defining a space between the first and second data surfaces, the space containing a gas, such that the light beam is selectively focussed through the first radiation transmissive member to one of the first and second data surfaces;
• an optical transmission means for directing the light beam from the light source to one of the data surfaces of the optical medium;
• and
• an optical reception means for receiving a reflected light beam from the optical medium and providing a data signal responsive thereto.

An optical data storage medium comprising:

• a first light transmissive substrate having a first light transmissive data surface for storing recorded data, the first data surface having marks which are optically detectable;
• a second substrate having a second data surface for storing recorded data, the second data surface having marks which are optically detectable;
• and
• a spacer means located between the first and second substrates for defining a space between the first and second data surfaces, the space containing a gas such that a light beam is selctively focussed through the first light transmissive member to one of the first and second data surfaces, the spacer means having a passage connecting the space with the atmosphere outside the medium, the passage allowing the movement of gas between the space and the atmosphere outside the medium and the passage blocking the movement of solid particles between the space and the atmosphere outside the medium.