Laser diodes (LD), also known as Light Amplification by Stimulated Emission of Radiation (LASER) diodes, are core components of laser ranging modules and laser distance sensors. They produce coherent light with precisely the same wavelength and phase, making them highly efficient.
Laser diodes offer several advantages, including their small size, lightweight design, low power consumption, and simple driving circuit. They are also known for convenient modulation and resistance to mechanical shock and vibration. However, laser diodes are sensitive to overcurrent, overvoltage, and electrostatic interference, so careful handling is necessary to avoid exceeding their maximum allowable parameters.
Here are some methods for driving laser diodes:
Constant Current Source: Use a DC constant current source, such as a circuit built with LM317, to drive the laser diode.
Current Limiting Resistor: Connect a current-limiting resistor in series with the laser diode circuit and a bypass capacitor in parallel for stabilization.
Heat Dissipation: Ensure proper heat dissipation measures are in place to maintain the diode within a safe temperature range. As the laser diode heats up, the current flowing through it can increase.
Reverse Voltage Protection: To prevent damage from excessive reverse voltage, fast silicon diodes can be connected in anti-parallel at both ends.
Laser diodes can directly modulate their output light intensity based on input current due to the mostly linear relationship between output optical power and input current. In practical applications, an Auto Power Control (APC) circuit is commonly used to drive the laser diode. This circuit employs a photodiode (PD) built into the same package to receive light from the LD, providing feedback and monitoring the output to maintain a consistent, required optical power.
The image below shows a simple laser diode APC drive circuit:
The following image shows a laser supporter added to the Meskernel laser distance module
