| 摘要 |
<p>PURPOSE:To measure a modulation level and reflection factor of an optical disc directly, by driving a laser in pulse by a pulse with the frequency more than doubling that of a recording signal to observe a reproduction output from a disc with an oscilloscope. CONSTITUTION:An oscillation circuit 4 oscillates and supplies a frequency signal with the frequency more than doubling that of a recording signal, namely more than doubling a reproduction spatial frequency, for example, 20MHz to a pulse generation circuit 5. A pulse signal obtained on the output side of the circuit 5 is supplied to a laser diode 7 through a laser diode driving circuit 6 to drive the diode 7 in pulse. In this case, the surface of an optical disc 3 is irradiated with laser light of about 10mW from the diode 7. Reflected light from the disc 3 is supplied to a beam splitter 13 and detection signals obtained with photodetectors 1a and 1b are observed with an oscilloscope 2, thereby enabling direct measurement of a modulation level and a reflection factor of the optical disc.</p> |
