Projection system and beam generating device and beam brightness control method thereof

The invention provides a projection system and a beam generating device and beam brightness control method thereof. The beam generating device comprises a first controller, a driver, a light emittingdevice, a sensing device, and a second controller. The driver generates driving current according to a control command. The light emitting device generates an output beam according to the driving current. The sensing device detects the driving current and the output beam to generate detection current and detection brightness. The second controller generates an adjustment signal according to the detection current and the detection brightness. The first controller or the second controller generates the control command according to an adjustment signal. The operation speed of the second controller is higher than the operation speed of the first controller. According to the invention, the adjustment signal for adjusting the driving current can be quickly generated. 投影系统及其光束产生装置及光束亮度的控制方法。光束产生装置包括第一控制器、驱动器、发光装置、感测装置以及第