OPEN-WLS

Summary

This project aims to bring optical experiment quality light sources to the student budget. Featuring a material cost of approximately $100, its incredibly competitive with industry Xenon sources and has a slew of quality of life features.

The entire system revolves around the fact that HID headlights are essentially identical to expensive Xenon arc lamps at a fraction of the cost.

The system is built around the supporting electronics, and features:

  • Lots of cooling!
  • Quick swap optical axis
  • Fuses for safety
  • Relay control with spring wire terminals
  • TPU feet
  • Easy to service case
  • Support for up to 100W bulbs

Optical System

Xenon bulbs are essentially the best option for optical white light sources. They feature a continuous spectral density from 200 – 1100nm and a color reproduction index (CRI) of approximately 100% (Class E).

The light source doesn’t quite live up to that promise, but does deliver high power throughout the visible range represented below.

Measured using spectrometer, 1ms integration time. Spectrometer consistently peaked when trying to measure infrared portion. Spectrum overlay: Bhutajata, CC BY-SA 4.0, via Wikimedia Commons

HID headlights and xenon gas discharge tubes operate by passing a high voltage between two electrodes exciting xenon gas to radiate. As a result the system uses a ballast to store up power and release a high voltage pulse, which the igniter passes to the bulb.

The system is designed with a hot-swappable optical axis in mind.

Most light sources simply project the light out of an aperture with no collimation. This is fine for fiber illuminators; however, most optical experiments start by collimating the light. This source takes out the middle man by using a parabolic SMO flashlight reflector. These reflectors are sub $10 and allow the relative collimation of the light, making the system far more efficient to collimate.

Collimated beam exiting the WLS.

Mounting this reflector on a locking lens tube allows the quick swapping between different optical assemblies, that way the user can make multiple configurations and rapidly swap the system to fit experiments. For example maybe one experiment needs a high power fiber coupler, and another needs collimation.

Materials & Models

Onshape File
Name / LinksQuantity$/perNotes
HID Bulb + Ballast + Igniter139D2S Bulb 35-50W
AC to DC Supply11624V 4A & 12V 1A, 100W
XL4015 DC to DC Buck Converter13.55A
HW-803 Relay125V from LM2596 set to normally closed
LM259611.3Set to 5V
8010 Fan11212V from supply
3010 Fan3212V from supply
AC Input Plug10.7IEC 320-C14 panel snap (no 3d model) (add before last step/wiring)
CLIFF 2P Spring Terminal14.5Connects to HW-803, used for relay control input (no 3d model) (add before last step/wiring), glue in place
SPST Rocker Switch10.9On/off for system
5x20mm Fuse Holder11.710A fast blow fuse recommended
SMO Reflector15.5Position arc at or behind focal point, will require modification for bulb to fit
M3-4mm Heatset14Soldering iron required to install
M4-4mm Heatset4Soldering iron required to install
M4-8mm Socket Bolt4Length between 8 and 18mm
M3-6mm Socket Bolt8Length between 4 and 6mm
M3-8mm Socket Bolt6
Bill of Materials

Construction

Place 3x M4 & 6x M3 heatset inserts.

Place 8010 fan, ballast, HW-803, LM-2596, fuse holder, switch, 3x M4-8mm bolts, & 4x M3-6mm bolts.

Place 8x M3 heatset inserts.

Place 4x 3010 fans, AC-DC supply, & 4x M3-6mm bolts.

Place DC-DC converter, igniter, & HID bulb.

Combine sides, optical axis, 4x feet, & 4x M3-8mm bolts.

System internals, note that the AC input and spring terminal is installed.
Electrical diagram of system, please reference the 3D models or BOM for more details.

Safety

The bulb gets really hot and emits heavily in the UV and IR.

So don’t touch the bulb directly, and don’t look at the source directly.

It is better to work in a light room so that your pupils are more closed and less light enters from reflection.