The common modes of lasers are divided into 4 main modes, which are as follows
- Mode 1 Internal control with suppression of the first pulse and indication light.
- Mode 2 Internal control with no suppression of the first pulse and no indication light.
- Mode 13 External control with suppression of the first pulse and indication of the light.
- Mode 15 External control with first pulse unsuppressed and no indicator light.
The difference between these four commonly used modes can be summarized in two points:
- Internal or external control.
- First pulse with inhibition, with indication light. First pulse without suppression, no indication light.
Internal control
Internal control means that the frequency and power coefficient (duty cycle) of the laser are generated internally by the laser, and the laser's output frequency and power can be controlled by the laser's host computer software or by sending serial commands.
In internal control mode, the laser factory default is GATE interface low level [i] light out, high level [ii] light off, so we in the internal control mode, if the GATE interface is in the state of hanging, the laser can be directly out of the strong light.
At the same time, in internal control mode, we can also invert the output level of the laser through the serial command GTR=1, so that the GATE interface can output light at high level and turn off light at low level.
[i] Low level is defined as 0-0.4V.
[ii] High level is defined 3.7-5V
External Control
External control means that the laser switches the light on and off and the frequency and power level of the light output are determined by an external PWM signal. By changing the frequency and duty cycle of the PWM signal, the frequency and power level of the laser's light output are controlled.
Under the external control mode, the factory default of the laser is to receive the PWM signal at the TRIG interface terminal that is out of the light, and in the case of a constant frequency of the PWM signal, the greater the duty cycle, the greater the output power of the laser. In addition, it must be ensured that the TRIG interface terminal is kept low under the no-light state.
At the same time, the external control mode can also be commanded through the serial interface PTR = 1 for PWM signal high and low level duty cycle inversion, into the PWM signal duty cycle, the greater the output power of the laser is smaller. In addition, it must be ensured that the TRIG interface terminal is kept high under the no-light state.
First Pulse Suppression and Indicator Light
The first pulse and the indication light of the laser are in the relationship of one and the other, for example, under MOD13, there is indication light, but the first pulse is the smallest, while under MOD15, there is no indication light, and the first pulse is the largest.
Difference and matching of GATE and TRIG signals
GATE Signal
The GATE signal of the laser corresponds to a TTL level signal, which is usually also called a switching gate signal; by default, the laser is at a high level for off and a low level for on;
There are only these two states in his working state, either high level or low level.
TRIG signal
The TRIG signal of the laser corresponds to the PWM pulse width modulation signal, which is usually called the repetition frequency signal; the PWM signal can be used for frequency modulation by changing the period of the pulses, and for voltage modulation by changing the width (duty cycle) of the pulses.
TRIG is bound to exist in the working state of the cycle frequency, and the greater the duty cycle the greater the voltage; the default state of the laser is the PWM signal high level energy storage, the falling edge of the light.
