Optical turntable system with reflected spot position detection

An optical turntable system for playing a phonograph record having a recorded signal, represented by first and second recorded signal components, in a spiral groove into the surface of the record where the groove is formed by said first and second walls where said walls intersect at approximately 90 degrees, each wall at an angle of approximately 45 degrees with respect to the surface of the record, each of said walls having lateral positions modulated by said first and second recorded signal components, respectively, said system comprising,

• a drive unit for rotating said record,
• an optical unit displaced from the surface of the record and adapted to be relatively moved with respect to the record, said optical unit having a detector,
• said detector including,
• a first optical source providing a first light beam incident onto said first wall to form a first incident spot and to provide a first reflected beam from said first wall reflected at a first reflected angle, proportional to said first recorded signal component, causing said the first reflected beam to be partially blocked by said second wall thereby resulting in a first blocked reflected beam component and a first non-blocked reflected beam component, said first non-blocked reflected beam component forming a first reflected spot having a first size determined as a function of the extent of blocking by said second wall,
• a second optical source providing a second light beam incident onto said second wall to provide a second reflected beam from said second wall reflected at a second reflected angle, proportional to said second recorded signal component, causing said second reflected beam to be partially blocked by said first wall thereby resulting in a second blocked reflected beam component and a second non-blocked reflected beam component, said second non-blocked reflected beam component forming a second reflected spot having a second size determined as a function of the extent of blocking by said first wall,
• a first optical sensor for sensing said first non-blocked reflected beam component to provide a first tracking signal proportional to said first size and to provide a first output data signal proportional to said first recorded signal component,
• a second optical sensor for sensing said second non-blocked reflected beam component to provide a second tracking signal proportional to said second size and to provide a second data output signal proportional to said second recorded signal component,
• difference means for subtracting said first and second tracking signals to form a tracking error signal,
• lateral servo means responsive to said tracking error signal for driving said optical unit to position said first and second light beams to be incident on said first and second walls, respectively, within said groove as said record is rotated relative to said optical system.

An optical turntable system for playing a phonograph record having a recorded signal, represented by first and second recorded signal components, in a spiral groove in the surface of the record where the groove is formed by first and second walls where said walls intersect at approximately 90 degrees, each wall at an angle of approximately 45 degrees with respect to the surface of the record, each of said walls having positions modulated by first and second recorded signal components, respectively, said system comprising,

• a drive unit for rotating said record,
• an optical unit displaced from the surface of the record and adapted to be relatively moved with respect to the record, said optical unit including a data detector, said data detector including,
• a first optical source providing a first light beam incident onto said first wall to provide a first reflected beam from said first wall at a first reflected angle proportional to the first recorded component, said first reflected beam forming a first spot,
• a second optical source providing a second light beam incident onto said second wall to provide a second reflected beam from said second wall at a second reflected angle proportional to said second recorded component, said second reflected beam forming a second spot,
• a first optical sensor for sensing the reflected angle of said first reflected beam by sensing the position of said first spot to provide a first output signal proportional to the first recorded component,
• a second optical sensor for sensing the reflected angle of said second reflected beam by sensing the position of said second spot to provide a second output signal proportional to the second recorded component,
• tracking means for positioning said optical unit so as to cause said first and second light beams to the incident on said first and second walls within said groove as said record is rotated relative to said optical system.

An optical turntable system for playing a record having a recorded signal in a groove where the groove is formed by a first wall and a second wall having positions modulated by the recorded signal where said first wall and said second wall intersect at an angle, each of said walls extending at an angle with respect to a plane formed by the surface of said record, comprising,

• first and second optical units including first and second optical sources and first and second optical sensors, said source providing first and second light beams incident to form first and second incident spots on said first and second walls and first and second reflected beams from said walls forming first and second reflected spots formed by first and second incident rays at said first and second optical sensors, respectively, with spot positions proportional to the recorded signals, said optical sensors for sensing the spot positions of said reflected spots to provide output signals proportional to the recorded signals, said first optical source providing the light beam incident onto said first wall at first incident angle with respect to an axis normal to the plane of said first wall at the point of incidence of said first beam whereby the reflected angle for said first reflected beam is proportional to said first incident angle and said first recorded signal, said second source and said second sensor positioned relative to said second wall such that one component of said second reflected beam is blocked by said first wall and such that a second component of said second reflected beam is not blocked by said first wall whereby said second detector signal is proportional to said second component of said second reflected beam,
• a tracking assembly for causing said light beam to be tracked with said groove as the record rotates, said tracking assembly including a vertical unit for positioning said optical unit a predetermined height from said record, said vertical unit including a vertical detector for detecting said predetermined height and for providing a vertical error signal as a function of the vertical displacement of the optical unit from said predetermined height and including vertical servo means responsive to said vertical error signal for tracking said optical unit at said predetermined height, said vertical detector including a vertical source for providing an incident vertical detector beam incident upon the record surface to provide a reflected vertical detector beam and including a vertical sensor positions to sense said vertical detector reflected beam, said vertical detector incident beam being approximately orthogonal to said first and said second incident light beams,
• a drive assembly for moving the record relative to said optical unit.