Optical transducer and recording/playback device comprising the transducer

Abstract

An optical transducer according to the invention comprises optical detection means ( 1 ) including a first ( 1 A ), a second ( 1 B ), a third ( 1 C ) and a fourth optical detector ( 1 D ), such that a first imaginary line ( 2 a ) from the third optical detector ( 1 C ) to the first optical detector crosses a second imaginary line ( 2 b ) from the second optical detector ( 1 B ) to the fourth optical detector ( 1 D ). The optical detectors generate detection signals (A,B,C,D) in response to an intensity of radiation incident thereon. The optical transducer further comprises signal combination means ( 4 ) for generating a first, a second, a third and a second combination signal. The first and the second combination signals (AC+, AC−) are indicative for the sum of the electrical detection signals (A,C) of the first ( 1 A ) and the third optical detector ( 1 C ). The third (BD+) and the fourth combination signal (BD−) each are indicative for the sum of the electrical detection signals (B,D) of the second ( 1 B ) and the fourth optical detector (1 D ). The first (AC+) and the second combination signal (AC−) have a mutually opposite phase. The third (BD+) and the fourth combination signal (BD−) also have a mutually opposite phase.

1 . Optical transducer comprising optical detection means ( 1 ) including a first ( 1   A ), a second optical detector ( 1   B ), a third ( 1   C ) and a fourth optical detector ( 1   D ), such that a first imaginary line ( 2   a ) from the third optical detector ( 1   C ) to the first optical detector crosses a second imaginary line ( 2   b ) from the second optical detector ( 1   B ) to the fourth optical detector ( 1   D ) which optical detectors generate detection signals (A,B,C,D) in response to an intensity of radiation incident thereon, the optical transducer further comprising signal combination means ( 4 ) for generating a combination signal which is indicative for a sum of electrical detection signals,  
       characterized in that 
 the combination signal (AC+) is indicative for the sum of the electrical detection signals (A,C) of the first ( 1   A ) and the third optical detector ( 1   C ), the signal combination means ( 4 ) further being comprised for generating a first (AC−), a second (BD+) and a third additional combination signal (BD−), the first additional combination signal (AC−) also being indicative for the sum of the electrical detection signals (A,C) of the first ( 1   A ) and the third optical detector ( 1   C ), the first additional combination signal (AC−) and the combination signal (AC+) having a mutually opposite phase, the second (BD+) and the third additional combination signal (BD−) each being indicative for the sum of the electrical detection signals (B,D) of the second ( 1 B) and the fourth optical detector ( 1 D), the second (BD+) and a third additional combination signal (BD−) having a mutually opposite phase.  
 
     
     
         2 . Optical transducer according to  claim 1 , characterized in that the optical detection means ( 1 ) further comprise a fifth optical detector ( 1   G ) which is arranged in a direction ( 3 ) from the first ( 1   A ) and the fourth detector ( 1   D ) to the second ( 1   B ) and the third detector ( 1   C ) of an imaginary line ( 2 ) beside the second ( 1   B ) and the third optical detector ( 1   C ) and a sixth optical detector ( 1   H ) arranged in said direction ( 3 ) beside the fifth optical detector ( 1   G ), the detection means ( 1 ) further comprising a seventh optical detector ( 1   F ) arranged in a direction opposite the first direction ( 3 ) beside the first ( 1   A ) and the fourth optical detector ( 1   D ), as well as an eighth optical detector ( 1   E ) arranged in a direction opposite the first direction beside the seventh optical detector ( 1   F ).  
     
     
         3 . Optical transducer according to  claim 1 ,  2 , characterized by input means for receiving one or more mode selection signals (S 1 , S 2 ), mode selection means ( 7 ) responsive to the one or more selection signals, which mode selection means enable a plurality of operational modes (M 0 , M 1 , M 2 , M 3 ), in which at least one output signal (RF 1+ ) is a selectable function of one or more of the electrical signals (A, B, C, D, E, F, G, H) generated by the optical detectors.  
     
     
         4 . Optical transducer according to  claim 3 , characterized by an operational mode (M 1 ), wherein a first (RF 1+ ) and a second output signal (RF 1+ ) each are representative for the sum of the electrical signals (A,B, C, D) of the first until the fourth detector ( 1   A ,  1   B ,  1   C ,  1   D ), the first (RF 1+ ) and the second output signal (RF 1+ ) being of opposite phase, a third output signal (RF 2+ ) being representative for the sum of the electrical signals (F,E) of the seventh ( 1   F ) and the eighth detector ( 1   E ), a fourth output signal (RF 2− ) being representative for the sum of the electrical signals (G, H) of the fifth ( 1   G ) and the sixth detector ( 1   H ). the fifth until the eighth output signal (VA, VB, VC, VD) respectively being representative of the electrical signals (A, B, C, D) of the first until the fourth detector ( 1   A ,  1   B ,  1   C ,  1   D ).  
     
     
         5 . Optical transducer according to  claim 3 , characterized by an operational mode (M 2 ), wherein a first (RF 1+ ) and the second output signal (RF 1− ) each are representative for the sum of the electrical signals (A, B, C, D) of the first until the fourth detector ( 1   A ,  1   B ,  1   C ,  1   D ) the first (RF 1+ ) and the second output signal (RF 1− ) being of opposite phase, the third output signal (RF 2+ ) being representative for the sum of the electrical signals (G, E) of the fifth ( 1   G ) and the eighth detector ( 1   E ), the fourth output signal (RF 2− ) being representative for the sum of the electrical signals (H, F) of the sixth ( 1   H ) and the seventh detector ( 1   F ).  
     
     
         6 . Optical transducer according to  claim 3 , characterized by an operational mode (M 3 ), wherein the first (RF 1+ ) and the second output signal (RF 1− ) each are representative for the sum of the electrical signals (A, C) of the first ( 1   A ) and the third detector ( 1   C ), the first (RF 1+ ) and the second output signal (RF 1− ) being of opposite phase, the third (RF 2+ ) and the fourth output signal (RF 2− ) each being representative for the sum of the electrical signals (B, D) of the second ( 1   B ) and the fourth detector ( 1   D ), the third (RF 2+ ) and the second output signal (RF 2− ) being of opposite phase.  
     
     
         7 . Optical transducer according to  claim 3 , characterized by an operational mode (M 0 ) wherein the first output signal (RF 1+ ) is representative for the sum of the electrical signals (A, B, C, D) of the first until the fourth detector ( 1   A ,  1   B ,  1   C ,  1   D ), the second until the fourth output signal (RF 1− , RF 2+ , RF 2− ) respectively are representative for the electrical signals of the eighth ( 1   E ), the seventh ( 1   F ) and the fifth detector ( 1   G ), a further output signal (VP) being representative of the electical signal (H) of the sixth optical detector ( 1   H ).  
     
     
         8 . Optical transducer according to one of the  claims 4  to  7 , characterized in that the fifth until the eighth output signal (VA, VB, VC, VD) respectively bare representative of the electrical signals (A, B, C, D) of the first until the fourth detector ( 1   A ,  1   B ,  1   C ,  1   D )  
     
     
         9 . Optical transducer according to  claim 8 , characterized by a first plurality of outputs (RF 1+ , RF 1− , RF 2+ , RF 2− ) having a relatively wide bandwidth and a second plurality of outputs (VA, VB, VC, VD) having a relatively small bandwidth, the first plurality of outputs being selected for the output signals having a mutually opposite phase.  
     
     
         10 . Device for recording and/or playing a record carrier comprising a write/read head ( 101 ) which includes an optical transducer ( 101 ) according to one of the  claims 1  to  9 , and an optical system for mapping at least one radiation beam via a scanning spot ( 102 ) at the record carrier ( 100 ) at the optical detection means ( 1 ) of the optical transducer ( 101 ), the device further comprising displacement means ( 103 ,  104 ,  105 ,  106 ) for displacing the scanning spot ( 102 ) with respect to the record carrier ( 100 ).