Oriel Cornerstone™ 260 1/4 m Monochromator
  • New, USB2.0 models
  • Operate two or three gratings simultaneously, individually replaceable
  • Dual output ports
  • Superior resolution and very low stray light
Print View
Technical Question
Share This Page
Feedback
DescriptionSpecifications Models Catalog PDF
Cornerstone 260 1/4 m Monochromator with a detector mounted to each output port

Why The Cornerstone 260?

Superior performance and ease of use at an economical price make the Cornerstone 260 Monochromator one of the best choices for UV-IR spectroscopy and radiometry. The dual grating instruments offer improved resolution, over the triple grating instruments. The grating mounts are interchangeable, so if you currently have a triple grating Cornerstone, you can easily convert it to a dual grating instrument for improved resolution in your spectral range of interest.

Optical Configuration

Fig. 1 shows the asymmetrical in-plane Czerny-Turner optical configuration of the Cornerstone 260. The input F/number is F/3.9. The resolution is 0.10 nm (dual grating instruments with a 1200 l/mm grating and 10 µm x 2 mm slit). Throughput is high and stray light is very low. We relied on our extensive research on optical flat black paints and baffles, and the use of high efficiency spherical mirrors and gratings to minimize surface reflections, and thus, stray light.


Fig. 1 Optical design of the triple grating Cornerstone 260 1/4 m Monochromator

Motorized Wavelength Drive

Cornerstone™ 260 uses a stepping motor drive to change wavelengths and to switch gratings. This direct drive mechanism slews at a maximum rate of 205 nm/s (with a 1200 l/mm grating). Wavelength precision with a 1200 l/mm grating is 0.08 nm. Grating switching takes only 10 seconds.

Stray Light

Stray light is very low in the Cornerstone™ 260 Monochromator. Here, we list two stray light tests. Both measurements were made using a UV-VIS photomultiplier, model 77340.

Measurement 1*

Using an Oriel Deuterium Source, measurements were made with and without a glass plate in the beam. The glass blocks all radiation below 320 nm. At 250 nm, the stray light signal was only 3 x 10-4 of the unblocked signal.

Measurement 2**

Using a HeNe laser at 632.8 nm focused on the slit in an F/4 cone, the average of the stray radiation readings at 612.8 and 652.8 nm was 1.5 x 10-5 of the signal at 632.8 nm. A 1200 l/mm, 500 nm blaze ruled grating was used.
*The comparison is based on a taxing but real measurement scenario, measuring monochromatic UV in the presence of a source producing scattered UV-VIS and a detector sensing it. The test is similar in principle to the ASTM E387 test used for spectrophotometers. The test first records the signal at 210 and 250 nm. Then, the entire real signal is blocked by insertion of a glass plate; what remains is scattered radiation.

**This measurement is primarily an indicator of the grating quality.

Two Output Ports

Cornerstone 260 has two output ports to allow continuous scanning over a broad wavelength range without breaking down the instrument to switch detectors. This switcher is commanded through the Cornerstone 260 software or hand controller. Note that with the help of model 77713 Motorized Beam Steerer (see Motorized Beam Steerers for Oriel Monochromators and Spectrographs), it is also possible to turn the monochromator into a dual input instrument.

Instrument Control

We offer Cornerstone 260 Monochromators with USB 2.0 or with RS232 and IEEE-488 interfaces. You can communicate with any of the Cornerstone 260 instruments in one of 3 manners.

Hand Controller

The 74009 Hand Controller is a dedicated interface just for the Cornerstone Monochromator Family. There is no need to memorize commands or key sequences; the 24 keys are clearly labeled with functions like “Step Up,” “Go Wave,” and “Shutter”. The backlit LCD display provides constant information on grating lines/mm, filter wheel position, current wavelength, and shutter status. The 74009 provides intuitive access to nearly all the functionality of the Cornerstone 260.

Computer Control

The computer interface was also designed for simplicity and ease of use. The Cornerstone ASCII command set is simple to use via RS 232 or GPIB. For example, close the shutter is “SHUTTER C” and change to the second grating is “GRAT 2”.

Complete Software Packages

We offer various software applications for Cornerstone™:
  • A simple utility program to get up and running right away (included with all Cornerstone 260 instruments)
  • For LabView programming we offer VIs (included with all Cornerstone 260 instruments)
  • TRACQ Basic™; this is an optional instrument control and data acquisition software package. It controls the Cornerstone 260, its accessories, the Oriel Merlin™ Digital Lock-in, and new Optical Power Meter. TRACQTM Basic lets you set the monochromator parameters, i.e. grating changeover point, data collection points, etc., and walk away while Cornerstone does the work.
  • TRACQTM Pro; this optional program is our advanced Radiometry Software Application; it is primarily used to complement our InstaSpec™ Benchtop Spectrometers, although it will control all Oriel Spectroscopic instruments (including the Cornerstone family of Monochromators).

Interchangeable Gratings

The Cornerstone 260 holds two or three gratings simultaneously. Each is mounted in its individual, prealigned mount. Simply drop it in place, and program the grating specifications into the Cornerstone through the Control/Utility Program or Hand Controller. If you intend to use the Cornerstone 260 as a triple grating instrument, choose your gratings from the “Triple Grating Assemblies” list in Table 1. If you intend to use the instrument as a dual grating monochromator, order two gratings from the “Dual Grating Assemblies” list.

Add Gratings in the Field

You can add and change gratings in the field without changing the instrument’s grating turret. However, you may have to replace your current grating assemblies. If you want to change a dual grating instrument into a triple grating instrument, you cannot simply order a third grating; all three of your gratings need to be Triple Grating Assemblies. Similarly, if you wish to convert your triple grating Cornerstone 260 to a dual grating Cornerstone 260 (to improve resolution), you can’t simply remove one grating; you will need to order two new Dual Grating Assemblies.

Table 1 Grating Specifications for Cornerstone 260 1/4 m Monochromator

These gratings are mounted in pre-adjusted holders that can be inserted and removed, at any time, from the Cornerstone 260.
 Line Density (I/mm)  Blaze Wavelength  Type  Reciprocal Dispersion (nm/mm)*  Peak Efficiency (%)  Primary Wavelength Region **  Instrument's Upper Wavelength Mechanical Limit
(for specificed grating)		  Model
 Dual Grating Assemblies  Triple Grating Assemblies
 2400  250  Holographic  1.6  60  180 - 700 nm  700 nm  74160  74060
 1800  500  Holographic  2.1  65  300 - 925 nm  925 nm  74161  74061
 1200  250  Holographic  3.2  80  180 - 650 nm  1400 nm  74162  74062
 1200  350  Ruled  3.2  65  200 - 1400 nm  1400 nm  74163  74063
 1200  1000  Ruled  3.1  80  550 - 1600 nm  1200 nm  77990  77989
 1200  750  Ruled  3.1  80  450 - 1400 nm  1400 nm  74164  74064
 600  200  Ruled  6.4  90  180 - 500 nm  2800 nm  74165  74065
 600  400  Ruled  6.5  80  250 - 1300 nm  2800 nm  74166  74066
 600  1000  Ruled  6.4  75  600 - 2500 nm  2800 nm  74167  74067
 600  1250  Ruled  6.4  70  750 - 2500 nm  2800 nm  74168  74068
 600  1600  Ruled  6.2  85  900 - 2800 nm  2800 nm  74169  74069
 400  1200  Ruled  9.7  80  700 - 2500 nm  4.2 µm  74170  74070
 400  1600  Ruled  9.6  80  900 - 2900 nm  4.2 µm  74171  74071
 300  500  Ruled  12.8  85  250 - 1150 nm  5.6 µm  74172  74072
 300  1000  Ruled  12.9  80  575 - 2500 nm  5.6 µm  74173  74073
 300  2000  Ruled  12.9  90  1100 - 5000 nm  5.6 µm  74174  74074
 246.16  226  Ruled  15.5  85  190 - 450 nm  6.8 µm  74175  74075
 200  1000  Ruled  19.3  85  600 - 2200 nm  8.4 µm  74176  74076
 150  300  Ruled  25.5  80  190 - 800 nm  11.2 µm  74177  74077
 150  800  Ruled  25.6  80  425 - 1600 nm  11.2 µm  74178  74078
 150  1250  Ruled  25.7  80  725 - 2800 nm  11.2 µm  74179  74079
 150  4000  Ruled  25.8  75  2.5 - 12 µm  11.2 µm  74180  74080
 121.6  413  Ruled  31.3  80  250 - 1000 nm  13.8 µm  74181  74081
 75  7000  Ruled  51.7  80  4.5 - 20 µm  22.4 µm  74182  74082

*At blaze wavelength.

**The primary wavelength region is where the grating efficiency is ≥20%. System efficiency will also be affected by the reflectivity of the mirrors and the grating angle at any wavelength.

Four Types of Slits

We offer four types of slit assemblies for the Cornerstone 260. Choose the same size and type of slit for the input and output of your monochromator. All our slit assemblies have a 1.5 Inch Series male flange.

Motorized Slit Assembly
  • Automated resolution control
  • Variable width from 6 µm to 3 mm
  • ±5 µm repeatability
  • 6 µm resolution
  • ±10 µm accuracy

This is our most versatile slit assembly. Change your instrument’s resolution by varying the slit width from 6 µm to 3 mm, in 6 µm steps. To operate a motorized slit, you also need the 74116 Slit Control Board; this board operates up to three motorized slits. Control is via the 74009 Hand Controller, or software. Input and output motorized slits are slightly different due to the mounting blocks. Please order motorized slits at the time you order the monochromator, so that we may factory install them. We do not recommend the installation of motorized slits in the field.

Micrometer Driven Slit Assembly
  • Continuously variable width from 4 µm to 3 mm
  • Continuously variable height from 1 to 15 mm
  • ±10 µm repeatability
  • ±10 µm accuracy from 4 to 250 µm, ±5% from 250 µm to 3 mm

The 74001 is a more economical choice than the motorized assembly, if you need to change resolutions frequently. It uses a precision micrometer drive to adjust the slit width from 4 µm to 3 mm.

Multiple Fixed Slit Assembly
  • 8 fixed slit positions from 50 µm to 3.16 mm
  • Slit height is adjustable from 1 to 12 mm

The 77269 is a rotating disc with eight highly repeatable fixed slit positions. A manual wheel rotates the disc to the desired slit width; each position has a positive detent for high repeatability.

Fixed Slits
  • Most economical for single slit size
  • Fixed width and height

If you only need a few slit sizes, this is the most economical choice. These are precision slits fixed on a machined slide. You need the 77294 Fixed Slit Holder to hold the slit and mate it to the monochromator.

Optional Motorized Filter Wheel

Choose the 74010 Motorized Filter Wheel to hold order sorting or neutral density filters. The 74010 holds six 1 inch (25.4 mm) diameter filters with no reduction in F/# (clear aperture, 0.87 inch (22 mm). Cornerstone™ 260 controls the 74010. Filter changeover is only 1.5 seconds for adjacent filters.

Simple Filter Interchange

With most filter wheels, you have to break down the setup to change filters, but with the 74010, the filters are held in individual mounts that snap into place from the top of the wheel. Six individual filter holders are included with each 74010 Filter Wheel. We also offer these separately under model 74011. Mount all your filters in 74011 Holders to protect them and have them ready for insertion into the filter wheel. The 74012 Rod Mount holds a 74011 Filter Holder atop an optical rod.

Built-In Shutter

We built a rugged, 0.5 Hz repetition rate shutter into the Cornerstone 260. The instrument drives the shutter; it is commanded via software or the hand controller. In addition to measuring background levels, the shutter is a convenient safety feature. You can close it when changing gratings or filters to protect your detector.

Shutter Specifications

Mounting

Cornerstone 260 is heavy enough (21 lbs; 9.5 kgs) to stand on its own with accessories mounted to the 1.5 Inch Series input and output slit assemblies. To simplify alignment of optical trains, order the 74105 Mounting Plate that bolts the Cornerstone 260 to inch (1/4-20) or metric (M6) optical surfaces. If you are coupling an Oriel Light Source into Cornerstone 260, order one of these kits:
  • 74102; couples 7340/7341 Dual Source into Cornerstone 260
  • 74104; couples 250 W Research Source into Cornerstone 260
  • 70632; couples Apex Illuminator into Cornerstone 260