Optical Elements for Spectroscopy
Useful links
This link takes you back to our spectroscopy page. This link will take you to the page for 3D printed parts.
Crossed Czerny-Turner Spectrometer configuration
The Wheetrometer is a spectrometer with a crossed Czerny-Turner configuration.
As shown in the figure on the left, light enters through an optical slit (bottom of figure) and passes to a collimating mirror at the top. After that, the light passes to a diffraction grating, then to a focusing mirror (on right) before it comes to the detector (on left). A good description of the Czerny Tuner optical bench is provided by B&W Tek.
Connecting to fiber optics
Optical fibers are not necessary but make it easier to connect your spectrometer to a light source and/or sample optics. Many optical devices use the SMA 905 connector which consists of the threaded flange (shown on left), a lens and a mounting system. As a lens, we use 5 mm fused silica spheres (known as a ball lens). Our mounting system is composed of a couple of plastic parts that you can print. One part is a spacer that goes between the connector and the ball lens. The other goes between the lens and the light source. The light captured seems to be relatively insensitive to the thickness of the spacer.
Ball Lens for fiber optics
We do not stock the ball lens but you can get them from Alibaba.com. We got ours from Changchun Worldhawk Optics Co., Ltd.
Optical Slit
One factor that limits a spectrometer's wavelength resolution is the width of the optical slit: Narrower slits give higher resolution. Our optical slits have a 0.1 mm width. This was the minimum that our source (Dongguan TMN Electronics Co., Limited) was able to make. If you wish to, you can purchase a narrower slit from a commercial source like this one. If you decide to go that way, be prepared to spend considerably more. You will also need to modify the slit mounting, but that is something I will help you with.
Collimating Mirror
The collimating mirror is a concave mirror that aligns the rays of incoming light parallel and reflects them toward the diffraction grating. This mirror is 20 mm in diameter with a focal length of 100 mm. Our mirrors were specially ground for us by a vendor we found through Alibaba. Changchun Yutai Optics Co., Ltd.
Diffraction Grating
Light dispersion uses a 12.7 mm square reflection grating. Gratings with a number of line densities are commercially available. We currently have a few in stock at 1200 and 600 lines/mm. You can get these cheaper from Alibaba. We got ours from Changchun Realpoo Photoelectric Co., Ltd.
Focusing Mirror
The focusing mirror is a rectangular concave mirror, 20 x 50 mm with a 50 mm focal length. It takes light diffracted at different angles and focuses it on the detector
