| 摘要 |
<p>A light source suitable for use with an image reader comprises a dielectric barrier discharge fluorescent lamp capable of emitting light in response to an external synchronizing signal without a variation in the amount of light. A phase comparator (13) compares the phase of an external synchronous signal (Sync) with the phase of a signal generated by a variable-frequency oscillator (11) and divided by a frequency divider (12), and controls the frequency of the variable-frequency oscillator (11) according to the phase difference. As a result, the phase of the variable-frequency oscillator (11) is locked to the phase of the external synchronizing signal (Sync). The signal from the variable-frequency oscillator (11) is supplied to a gate signal generator (5), the output from which turns on and off a switching element in an inverter circuit (3) to convert DC voltage from a DC source (5) to AC voltage. The AC voltage output from the inverter circuit (3) is applied to a lamp (1) through a stepup transformer (2) to light the lamp (1).</p> |
