The Oriel Mini-monochromators are low cost, compact and simple-to-use instruments for moderate resolution applications and are ideal for general laboratory experiments and educational studies covering fixed wavelength ranges and not requiring sub-nanometer resolutions. The focal length of these instruments is 74 mm; the F/# is 3.9.
For demanding spectroscopy applications, please refer to our long focal length, MS257™ 1/4 m Monochromator and Imaging Spectrograph.
Manual and Motorized Versions
Oriel offers two families of Mini Monochromators:
Manual Monochromators
These models have a knurled knob, which causes a precision lead screw/sine bar mechanism to rotate the grating. A digital counter displays the wavelength in nanometers, to 0.2 nm.
Motorized Monochromators
For scanning applications, we recommend that you choose a motorized monochromator. These instruments use a stepping motor driven by an external motor controller with a USB interface. Included with the controller is an application program with over 25 commands to control a variety of operations of the grating drive. These motorized models also include a manual drive and a digital counter that displays the wavelength to 0.2 nm.
Fig. 1 Optical configuration of Mini Monochromator
Optical Configuration
Fig. 1 shows the Ebert-Fastie design of these monochromators. Full spectrum radiation is focused at the entrance slit and reflected by a folding mirror onto a spherical collimating/focusing mirror. This mirror collimates the radiation and directs it onto the grating, where it is diffracted.
Once diffracted, the radiation is directed back to the collimating/focusing mirror, and a segment of the dispersed radiation is focused at the exit slit via a second folding mirror.
Four Wavelength Ranges
To keep the cost and size of these instruments down, we simplified the design. Unlike our fully featured higher-end Oriel Monochromators, these models have one fixed grating and the grating cannot be interchanged in the field. The grating is a 20 x 20 mm holographic or ruled grating (instrument dependent).
To cover the UV-NIR spectral range, we offer four models (in manual and motorized versions). These are listed in Table 1. As custom instruments, we can also offer instruments to cover the 750 nm to 1.7 µm and 850 nm to 2.2 µm regions.
Table 1 Wavelength Ranges of Mini Monochromators
|
Wavelength Range |
Grating Specifications |
|
Line Density (I/mm) |
Blaze Wavelength |
Grating Type |
| 190 - 650 nm |
2400 |
250 |
Holographic |
| 200 - 800 nm |
1800 |
250 |
Holographic |
| 300 - 800 nm |
1800 |
500 |
Holographic |
| 500 nm - 1.2 µm |
1200 |
750 |
Ruled |
Resolution
The resolution of the instrument is a function of its focal length, the dispersion of the grating, the width of the entrance and exit slits, and to a lesser degree, wavelength. Resolution is inversely proportional to slit width. As the slit width decreases, the resolution increases. Throughput, however, varies directly with the square of the slit width. Halving the width of the slit decreases throughput by a factor of four.
As standard models, these instruments include two 300 µm x 4 mm slits. You can increase the resolution by using narrower slits (we offer optional 50 µm, 100 µm, 150 µm, 600 µm and 1000 µm wide slits). You can request different slits at the time of purchase, or purchase extra sets so you can vary the throughput and resolution. The slits are easily interchangeable. Table 2 shows the resolutions possible with the standard and optional slits.
Table 2 Resolution of Mini Monochromators
|
Instrument's Usable Wavelength Range |
Linear Dispersion (nm/mm) |
Resolution With These Slits (nm)* |
|
50 µm |
100 µm |
150 µm |
300 µm |
600 µm |
1000 µm |
| 190 - 650 nm |
5.54 |
0.28 |
0.55 |
0.83 |
1.66 |
3.32 |
5.54 |
| 200 - 800 nm |
7.41 |
0.37 |
0.74 |
1.11 |
2.22 |
4.44 |
7.41 |
| 300 - 800 nm |
7.21 |
0.36 |
0.72 |
1.08 |
2.16 |
4.32 |
7.21 |
| 500 nm - 1.2 µm |
11.29 |
0.56 |
1.13 |
1.69 |
3.39 |
6.77 |
11.29 |
Stray Light
The amount of stray radiation exiting the slit of any monochromator depends upon various factors. These include: the grating, the operating wavelength and the scattering of light inside the instrument. The measured signal due to stray light also depends, and these are often the dominant factors, on the intensity and spectral distribution of the input source, and on the detector's spectral response. The stray light performance of these instruments is impressive: 0.03%.
Optional Accessories
Oriel offer various accessories specifically for these Mini Monochromators (note: these accessories cannot be used with our fully featured instruments.)
Order Sorting Filters
Block the unwanted higher order artifacts with an order sorting filter. Because of the unique input slit assembly of these monochromators, you cannot use our traditional flanged filter assemblies with these instruments. The assemblies for these monochromators have an integral slit; simply replace the entrance or exit slit assembly of the instrument, with a filter assembly. The filter assemblies come standard with 300 µm slits (as do the instruments).
Fig. 2 Transmittance of Order Sorting Filters
Fiber Optic Assemblies
As with the filter assemblies, dedicated fiber assemblies are needed for these monochromators. Our flanged fiber adapters will not mount to the slit assemblies of these Mini Monochromators.
We offer two glass fiber bundles for these instruments. One end of the bundle has an integrated 600 µm x 4 mm slit, which replaces the slit assembly on the instrument. The other end of the 78040 Fiber Assembly has a 4.8 mm OD ferrule. The other end of the 78041 Fiber Assembly has an SMA termination. Both fiber bundles are 5 ft (1.5 m) long.
Fig. 3 Transmittance of 78040 and 78041 Glass Fiber Bundles
Tunable Source
Build a tunable source with one of our Mini Monochromators and the 78042 or 78043 Tungsten Halogen Light Source. Each source includes:
- 20 W Tungsten Halogen Lamp
- 12 V DC power supply
- Variable aperture assembly
- Mounting baseplate
The spectral output of the source is 340 nm to 3 µm, and is matched to the entrance slit of the monochromator. The lamp housing, shutter and variable aperture assembly are mounted onto a baseplate, which allows you to attenuate the light or close off the beam with a simple manual slide.
The mounting baseplate accepts any Oriel Mini Monochromator model and aligns the source output so that it is focused onto the entrance slit of the monochromator – no alignment or secondary focusing optics are necessary.
Fig. 4 Throughput of 78022 Monochromator illuminated by 78042 Tungsten Halogen Source, at various slit widths.
