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Monday, August 9, 2021

Laser Diode Relative Power and Focus Measurement Tools

Measuring Relative Laser Diode Optical Power

As I study my new Vigotec VG-7X it seems that being able to measure the Diode's relative optical power would be a useful tool.

This tool could be used to:

Find the Focal Point

Adjusting the vertical position of the head over a fixed optical sensor should give a varying amplitude from the Opt101. The highest amplitude would be the FL. That is the point at which the power density is the highest.

Measure Relative Power Over Time

It would be useful to know what the power variation over time is. An amplitude measurement is taken at the FL and then compared to the same measurement over the machine's life.

Optical Power vs Current Characteristic Curve

Measure the amplitude at the FL and then vary the current to the Laser. Plot the characteristic curve for current vs power. This can be done with static current or current controlled by PWM.

Measuring the Diodes Optical Output

CJMCU101 Opt101 Module

I found an optical module that may allow the above measurement:

This module uses the OPT101 Monolithic Photodiode and Single-Supply Transimpedance Amplifier as the main component. Use this data sheet and the schematic I created to configure the module to meet your needs.

I don't know yet if there is enough response at the wavelength of the engraver's laser diode to produce a useable output with this device. Spec sheet says it is usable from 300-1100 nm.

CJMCU101 Schematic

I traced the board's circuit and the schematic for the module is here:

Click below to see the embedded schematic.


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