8/4/2019 Laser Power Meter 11

1/8

Laser Power Meter KP-360

Its is a typical example of an old way of making a systemIt shows the use of a lock-in amplifier

It shows the use of a trans-impedance amplifierIt shows a way of switchable amplification with discrete componentsIt shows many small points of interest to sensor and microsystem design.

Purposes of the study of this System!

!

!

!

!

Vrije Universiteit Brussel

Temporary lecture notes. by Prof. M. Kuijk (VUB) and Prof. H. Desmet (UGent)Sensors and Microsystem Electronics

8/4/2019 Laser Power Meter 11

2/8

Incident

interfering light

Vrije Universiteit Brussel

Temporary lecture notes. by Prof. M. Kuijk (VUB) and Prof. H. Desmet (UGent)Sensors and Microsystem Electronics

8/4/2019 Laser Power Meter 11

3/8

Operation

!

!

!

!

The optical measurement system is intended to allow a user to set up an experimentwhereby the user wants to know how much light is getting through its system, withoutmeasuring the ambient light (light that is present in the room).

The light has therefor to pass through a chopper. This is a mechanical system that issimilar to a ventilator. The blades will let the light through during a first period, and will thenblock the light, during a second period. In that way the light incident to the experiment will bemodulated. In this system the light is chopped at 33 Hz.

The measurement system will receive all incident light but will electronically discriminate

between the interfering light and the usefull light.

Typically, ambient interferers have a frequency of 0Hz (DC) and 100 Hz (in Europe).

Vrije Universiteit Brussel

Temporary lecture notes. by Prof. M. Kuijk (VUB) and Prof. H. Desmet (UGent)Sensors and Microsystem Electronics

8/4/2019 Laser Power Meter 11

4/8

Power supply system

Question: What are all these components for ?

Vrije Universiteit Brussel

Temporary lecture notes. by Prof. M. Kuijk (VUB) and Prof. H. Desmet (UGent)Sensors and Microsystem Electronics

8/4/2019 Laser Power Meter 11

5/8

Optical Head internal electronic circuit

Vrije Universiteit Brussel

Temporary lecture notes. by Prof. M. Kuijk (VUB) and Prof. H. Desmet (UGent)Sensors and Microsystem Electronics

8/4/2019 Laser Power Meter 11

6/8

Optical Head internal electronic circuit

Amplifier

Offset compensation path

TransImpedance Amplifier

Vrije Universiteit Brussel

Temporary lecture notes. by Prof. M. Kuijk (VUB) and Prof. H. Desmet (UGent)Sensors and Microsystem Electronics

8/4/2019 Laser Power Meter 11

7/8

Gain selector

Offset Compensation

Switchable GainMixer

Vrije Universiteit Brussel

Temporary lecture notes. by Prof. M. Kuijk (VUB) and Prof. H. Desmet (UGent)Sensors and Microsystem Electronics

8/4/2019 Laser Power Meter 11

8/8

Vrije Universiteit Brussel

Temporary lecture notes. by Prof. M. Kuijk (VUB) and Prof. H. Desmet (UGent)Sensors and Microsystem Electronics