Abstract: The present application discloses a device and method for harmful gas detection in tunnel advance drilling, which relates to the technical field of tunnel construction. The device for harmful gas detection in tunnel advance drilling comprises a casing pipe, and the casing pipe is provided with a laser monitoring module, used for emitting laser axially in the casing pipe, ranging, and monitoring harmful gas concentration; the casing pipe is provided with an occlusion module for periodically blocking laser emitted by the laser monitoring module; and the casing pipe also includes a gas flow rate monitoring module for monitoring the flow rate of harmful gas within the casing pipe. The present application enables accurate detection of harmful gas concentration at the bottom of advance drill hole, providing reliable data for risk assessment of harmful gas in the tunnel.

Abstract: A laser projection apparatus comprising a laser unit (40), a light modulation device (50), a projection lens (60), a display control circuit (20), and a laser unit control circuit (30). The laser unit control circuit (30) comprises a controller (31) and a driving circuit (32), the controller (31) being used for generating control signals on the basis of the light source driving signal, and the driving circuit (32) being used for generating, on the basis of the control signals, a power supply signal for supplying power to the corresponding laser unit (40). The control signals comprise a first control signal and a second control signal, the first control signal being a constant-level signal and the second control signal being a PWM signal.