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DMc150 Double Monochromator

  • DMc150 compact double monochromator

Comprising twin 150mm focal length Czerny Turner single monochromators operating in tandem with additive dispersion, the DMc150 offers exceptional optical performance within a small footprint.

Compatible with the full range of sources, detectors and entrance optics of the Bentham portfolio, the DMc150 is at the heart of many of our light measurement solutions including those for:-

  • Type-testing of tanning appliances
  • Accurate dosimetry of sources used in phototherapy (including PDT and PUVA)
  • Monitoring of solar UV irradiance
  • NVIS compatibility testing



  • Comprises twin 150mm focal length monochromators
  • Built in a single casting, for optimised rigidity and robustness
  • Stepping motor and sine bar driven diffraction gratings
  • Predictable sinusoidal wavelength accuracy
  • One entrance and up to two exit ports with automated mirror-based port selection for use of multiple input/ output configurations
  • Control electronics integrated and fully automated via USB 2.0 interface

Optical Layout

ConfigurationPair symmetrical Czerny Turner monochromators, additive dispersion
Focal lengthTotal focal length: 300mm
Individual Units: 150mm
Grating mountKinematic
Number of gratings1 pair
Grating size33x33mm
Aperture ratiof/4
Number of entrance/exit ports1 entrance, 1-2 exits
Spectral rangeWithin range 200nm-2400nm


Wavelength scanningBy integrated stepping motor and micro-stepping drive electronics
Slit typeFixed, micrometer or motorised variable
Slit width & height10µm-10mm (W) x 20mm (H)
Filter size- 6 position filter wheel : 25mm diameter
- 8 position filter wheel : 22mm diameter

Optical Performance (quoted for typical 2400 g/mm gratings)

Spectral range200-600nm
Linear dispersion5.4nm/mm
Wavelength accuracy± 0.15nm, ± 0.05nm with software correction
Wavelength reproducibility± 0.05nm
Resolution full/reduced slit height0.25/0.1nm
Stray light rejection at 2.5 FWHM10-8
Wavelength acquisition speed30nm/s


Computer interfaceUSB 2.0
Software controlBenWin+/SDK

Diffraction Gratings

A range of gratings are available depending on the spectral range of consideration. Diffraction gratings are supplied in pairs, on kinematic mounts to permit easy installation in the DMc150 without compromising the wavelength calibration.

GratingLine density (g/mm)Grating type & Blaze wavelength Maximum wavelength range (nm)
GA-G1524H0U252400Plane holographic, 250nm blaze200-600
GA-G1518H0U251800Plane holographic, 250nm blaze200-800
GA-G1518R0U51800Plane ruled, 500nm blaze200-800
GA-G1512R0U41200Plane ruled, 400nm blaze300-1,100
GA-G1512R0U51200Plane ruled, 500nm blaze300-1,100
GA-G1512R0U751200Plane ruled, 750nm blaze450-1,100
GA-G15083R1U2830Plane ruled, 1.2µm blaze650-1,700
GA-G1506R1U25600Plane ruled, 1.25µm blaze800-2,400
GA-G1506R1U6600Plane ruled, 1.6µm blaze800-2,400

Order Sorting

A filter wheel is located behind the entrance slit of the DMc150 to accommodate a shutter and long pass filters as required for the spectral range of operation. A six position filter wheel, for 25mm diameter filters is fitted as standard. An eight position filter wheel, for 22mm diameter filters is required where more positions are required.

Spectral rangeRequired OS filter
<400 nmUnder standard conditions- none required
Under purged operationOS310

Slit Configuration

The DMc150 can be configured in the compact, in-line or dual layouts. In the latter case a solenoid-driven programmable swing away mirrors (SAM), controlled by the internal drive electronics, is fitted for port selection.

Slit Type

The dimension of the largest of the entrance/ exit slits defines the bandwidth of the monochromator. Fixed, micrometer variable and motorised variable slits are offered, with a slit height of 20mm. For tuneable light source applications a range of exit slit apertures are available. Please enquire for further information.

Slit typeFeatures
Fixed slits (FSS)- Manually controlled
- Spring leaf to ensure the correct placement of the slit
Micrometer variable slits (VSS)- Manually controlled
- Bi-lateral slits
- Variable from 10µm to 10mm
Motorised variable slits (MVSS)- PC control via USB
- Driven via internal monochromator electronics or external MAC electronics bin
- Comprising stepping motor driven bi-lateral slits
- Variable from 10µm to 10mm

Further Options

Neutral density filtersA range of metallic neutral density filters, for installation in the DMc150 filter wheel, are available for the purposes of signal attenuation.
Purge portInstallation of purge ports on DMc150 to enable purging of the space within the monochromator for VUV work.

Monochromator Dimensions

DMc150 double monochromator front dimensions
DMc150 monochromator profile - Front profile
DMc150 double monochromator side dimensions
DMc150 monochromator profile - Side profile
DMc150 double monochromator top dimensions
DMc150 monochromator profile - Top profile

Software Control

The DMc150 may be controlled over the USB 2.0 interface using our Windows application Benwin+ or by user written code based on our SDK on a wide range of platforms (Labview, Matlab, C++ etc. Using configuration files, both applications allow:

  • Accessing grating, filter wheel and slit properties
  • Wavelength selection
  • Spectral measurements

Benwin+ includes higher functionality including:-

  • Easy system calibration
  • Obtain spectrally integrated (and weighted) quantities
  • Instantly obtain colorimetric data
  • Perform transmission, absorption and reflection measurements
  • Perform simple arithmetic functions
  • Utilities for control of translation stages, goniometers, RSB, data acquisition from other instruments etc.

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