Optical scanner, image display apparatus having optical scanner and driving method of optical scanner

An optical scanner comprising:

• a scanner base body including:
• a deflection mirror configured to deflect incident light in a predetermined direction;
• a support beam extending from the deflection mirror and supporting the deflection mirror;
• and
• a fixing part, to which an end of the support beam is connected;
• a drive unit configured to rotationally oscillate the deflection mirror and the support beam, thereby driving the scanner base body;
• a deflection status detector configured to detect a deflection status of the deflection mirror;
• and
• a controller configured to generate a drive signal for driving the scanner base body with a drive frequency and configured to transmit the drive signal to the drive unit,
• wherein the scanner base body is configured to:
• have a first resonance frequency and a second resonance frequency higher than the first resonance frequency,
• resonate at the second resonance frequency when the drive frequency is increased from a frequency lower than the first resonance frequency,
• resonate at the first resonance frequency when the drive frequency is decreased from a frequency higher than the first resonance frequency, and
• exhibit a dropping phenomenon that the deflection status is decreased when the drive frequency exceeds the second resonance frequency while the scanner base body is driven at the second resonance frequency, and
• wherein the controller includes:
• a first upsweep unit configured to upsweep a drive frequency of the drive signal from a frequency lower than the first resonance frequency;
• a dropping phenomenon detector configured to detect the dropping phenomenon based on a detection result of the deflection status detector;
• a target drive frequency determination unit configured to, when the dropping phenomenon detector detects the dropping phenomenon at a drive frequency during the upsweeping by the upsweep unit, determine a frequency lower than the drive frequency at which the dropping phenomenon is detected, as a target drive frequency;
• a second upsweep unit configured to upsweep the drive frequency of the drive signal toward the target drive frequency from a frequency lower than the first resonance frequency after the operation of the target drive frequency determination unit;
• and
• an adjustment unit configured to adjust the drive frequency of the drive signal so as to keep the deflection status at the target drive frequency based on the detection result of the deflection status detector after the operation of the second upsweep unit.