Scanning light measuring apparatus

A scanning light measuring apparatus for observing light scanned in a main scanning direction with controllable light-emission time and scanning speed by an optical unit having a synchronous detection sensor that detects the light, the apparatus comprising:

• a support table on which the optical unit is placed;
• a light-emission control circuit configured to control the light-emission time based on a synchronous detection signal from the synchronous detection sensor;
• a light-receiving element configured to receive the scanning light;
• a moving mechanism configured to support the light-receiving element so as to be movable in the main scanning direction and a rotation direction around an axis orthogonal to the main scanning direction and an optical axis direction of the scanning light;
• and
• a measurement control circuit configured to move the light-receiving element in the main scanning direction by the moving mechanism, scan the light-receiving element with the scanning light, acquire an output of the light-receiving element, and measure a scanning light diameter of the scanning light based on the output.