| 摘要 |
PROBLEM TO BE SOLVED: To realize an optical head which is thin, high in quality of record/ reproduce signals and can reproduce them at high speed. SOLUTION: δ% of a quantity of light of the light reflected by a medium is reflected by a second inner face of a prism 4, and (100-δ)% of the quantity of light passes the second inner face. The light reflected by the second inner face is received by a front light-receiving part of a photodiode chip 3. The light passing through the second inner face is reflected by a first inner face, and enters again the second inner face. (100-δ)% of the light passing through the second inner face is received by a central light-receiving part. δ% of the light reflected by the second inner face is reflected by the first inner face and received by a rear light-receiving part. When an optical path length between the first inner face and the rear light-receiving part is (a), an optical path length between the second inner face and the front light-receiving part is (b), and an optical path length between the first inner face and the second inner face is (c), a laser diode chip 1 is arranged to make an optical path length between the laser diode chip 1 and the first inner face (a+b+c)/2. |
