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   Hobby Projects
In my spare time I like to make videos on technical subjects, which are published on the Huygens Optics Youtube Channel. Below you will find a list of the video projects of the past year.

Etching tiny patterns in glass using hydrofluoric acid (HF) Dec 16, 2020   
This video contains an overview of some glass etching experiments I did with Buffered Oxide Etch (HF / NH4F). Just for the record: the video is not meant as an encouragement to start experimenting with concentrated HF yourself.

Making Optical Logic Gates using Interference Jan 16, 2021   
In this video I am looking into the idea of using optical interference to construct different kinds of logic gates, both from a conceptual- as well as from the practical perspective.

HUYGENS CHRISTMAS SPECIAL: Analog Television Equipment (& Nostalgia) Dec 16, 2020   
This video is a bit different from my previous videos and not related to optics. I made it purely out of interest for older (analog) equipment and technology. It discusses the principles behind analog TV transmission technology, such as color encoding in composite video signals and RF transmission and modulation methods.

Photons in Radio Waves and Visible Light Oct 30, 2020   
Experiments with interference of radio waves and visible light. This video shows single-photon interference with a variable path length and offers a explanation for this amazing phenomenon in the relativistic behaviour of the photon. In the video I also discuss "2-photon" interference, by which I actually refer to "multi-photon" interference, because this type of interaction will generally not limited to just 2 photons.

The Real Double Slit Experiment. Oct 5, 2020   
This video gives a different perspective on a more than 200 years old experiment and discusses in detail both the experiment itself, as well as the quantum mechanics behind it. In the video I show you how you can use a microscope to visualize the wave propagation and the development of the spatial probability distribution for the multi- and single photon experiment.
WARNING: do not attempt to repeat this experiment without using a camera! Looking at laser beams under a microscope with your bare eyes instead of a camera can kill your eyesight instantly and leave you blind for the rest of you life.

Building a Small Cleanroom for Photolithography. Sep 17, 2020   
This video describes the design- and build process of a small cleanroom space for my workshop. In addition to facilitating working more cleanly, it also allows for working with dangerous substances, such as strong fuming acids, and can be used for processing photoresists. It's build from approx. 5m2 of trespa plate material and uses a HEPA filter and a fan to achieve a steady supply of clean air.

Fourier Optics used for Optical Pattern Recognition Jul 25, 2020   
Optical Fourier transformations were performed using small lithographic patterns of different characters. A DLP projector can be used as a Fourier filter to do simple pattern recognition.

Light Waves Visualized using Photon Sieves. Jun 29, 2020   
The video shows how the optical wave front of a laser beam can be shaped by means of DIY photon sieves. It also shows how the quality and sharpness of the focal point in a diffraction pattern can be influenced by the number of diffractive apertures in the photon sieve surface.

Making a Mirror with a Variable Surface Shape. Jun 14, 2020   
Video about making a small glass-ceramic mirror with a variable surface shape. Some concepts in this video have been pictured in a somewhat simplified manner to make it more accessible to a less specialized audience.

Making Tiny Fresnel Lenses (in Times of Corona). Apr 5, 2020   
This video shows several types of micro-lenses that I made using a DIY maskless wafer stepper. The tiny lenses can for example be used for building a Shack-Hartmann wavefront detector.

Maskless Wafer Stepper Part 3: Elecronics and Software. Feb 10, 2020   
This is the third (and final) video on the DIY maskless wafer stepper project. It discusses the electronics and software.

Micro Lenses made with Photolithography. Feb 6, 2020   
I'm quite excited to show you the focal properties of the microscopically small lenses that I made using photolithography. These lenses are actually Fresnel zone plates which use diffraction as the method for focussing the light. They were made using the DIY maskless wafer stepper. The lenses have more than one focal plane, and you can easily observe the 1st, 2nd and 3rd order focal planes when they are used in combination with monochromatic light sources.

Maskless Wafer Stepper Part 2: Mechanics Jan 25, 2020   
This video is the 2nd of 3 video's on the design and build process of a small maskless wafer stepper. It discusses the mechanical aspects of the machine, in particular the challenges that I face to achieve the requirements. I also show some crude footage of the first optically active devices.

Maskless Wafer Stepper Part1: Optics Jan 4, 2020   
I've been planning to make a maskless wafer stepper for a long time. In the last few months, I finally found the time! This video is the first of 3 video's on the design- and build process. It discusses the optical aspects of the machine.

How to make Very Flat Optical Surfaces on Glass Dec 16, 2019   
The video shows (hands on) how a nanometer level flat optical surface can be made. It first discusses the principle of the continuous pitch polisher, also known as the planetary polisher or optical lap master.

Metal Detector Discrimination Explained (with a Garret AT Pro) Nov 12, 2019   
In this video I discuss the principle of a VLF- type induction balanced metal detector (Garrett AT pro), in particular how the discrimination between different metals works. I do this by looking at the emitted and received signals of a test coil, so not by opening up the detector.

Next Level Spirit Level (for billiard / pool table) Oct 14, 2019   
Leveling a billiard table to an exact horizontal orientation requires a very accurate "spirit level" device (also called "bubble level"). In this video I show the complete process, from requirements and design, to prototype manufacturing of the bubble level from 2 borosilicate glass disks.

Optical Lens Centering using a LOH LZ-80. Oct 8, 2019   
Unfortunately it turned out that -after my Loh LZ-80 centering machine was brought back to operational status- the lenses were already correctly centered. The cause for their poor performance was actually in the construction of the optical tube holding the triplet. So in the end, centering of the lenses turned out to be unnescessary.

Polishing a Small Spherical Mirror Surface on a Glass Blank Sep 17, 2019   
This video is a follow-up from the video on spherical radius grinding. In this video I explain briefly the grinding process (using sIlicon carbide, SiC) and polishing process (using Cerium oxide, CeO and optical pitch).

CNC Radius Milling in Optics: the LOH Spheromatic Curve Generator. May 30, 2019   
In this video I discuss spherical radius milling of both metal and glass. In addition the principle of the Loh Spheromatic CNC 120 radius grinder / mill is discussed. This machine can be used to mill / grind spherical surfaces on glass and ceramic objects.

DMD Mirrors in a DLP-Projector Moving in Slow Motion (Stroboscopic Effect). May 9, 2019   
This video shows how you can view in slow motion the very tiny digital micro mirrors that can be found in for example DLP-projectors (beamers). The method used here is based on a combination of microscopy and stroboscopy and does not require a high-speed camera. By using this method, we cannot only look at the pixels in real time but at the same time slow down the switching process (which is in the microsecond time range) by several orders of magnitude.

DIY Photolithography using 1980s Carl Zeiss S-Planar Lens (405nm). Apr 13, 2019   
In this video I demonstrate how I used a Carl Zeiss S-planar wafer stepper lens to do micron-size photolithography and used this pattern to etch a chromium layer.