Light source device and control method of light source device

A light source device comprising:

• a semiconductor light source;
• a light source control section that controls a light quantity per cycle period of light to be emitted from the semiconductor light source, by controlling a current supplied to the semiconductor light source through:
• (A) adjusting a current value for the semiconductor light source over a whole cycle period in response to the light quantity per cycle period being higher than or equal to a predetermined value, and (B) adjusting a period of supplying a minimum current to the semiconductor light source by pulse width modulation in response to the light quantity per cycle being lower than the predetermined value;
• an optical sensor that receives the light emitted from the semiconductor light source to acquire a quantity of the received light;
• a sensor control section that controls the optical sensor to detect the light in an exposure period shorter than a minimum pulse width where the semiconductor light source is turned on by the pulse width modulation in any cycle period, thereby acquiring the quantity of the received light which is acquired by the optical sensor;
• and
• an intensity adjusting section that adjusts emission intensity of the semiconductor light source on the basis of the quantity of the received light, wherein:
• (i) the light source control section causes a light source driver to stop supplying current to the light source at the end of the cycle period, and the sensor control section causes the light sensor to stop measuring the received light at the end of the cycle period in any cycle period, or
• (ii) the light source control section causes the light source driver to start supplying current to the light source at the start of the cycle period, and the sensor control section causes the light sensor to start measuring the received light at the start of the cycle period in any cycle period.